Let's do some math ..  Rounding examples of 7 random hypothetical purchases:
Case	Tag   Price	Sales   Tax %	Raw Total   Incl. Sales Tax	Rounded   to Penny	Rounded   to Nickel	Rounded   to Dime
Purchase #1	$210.48	10.858%	$233.3339	$233.33	$233.35	$233.30
Purchase #2	$101.85	9.540%	$111.5665	$111.57	$111.55	$111.60
Purchase #3	$118.61	8.137%	$128.2613	$128.26	$128.25	$128.30
Purchase #4	$142.50	9.173%	$155.5715	$155.57	$155.55	$155.60
Purchase #5	$228.36	3.557%	$236.4828	$236.48	$236.50	$236.50
Purchase #6	$129.76	3.102%	$133.7852	$133.79	$133.80	$133.80
Purchase #7	$168.63	13.836%	$191.9616	$191.96	$191.95	$192.00
7 purchase totals =	$1,100.19		$1,190.9628	$1,190.96	$1,190.95	$1,191.10