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	$206.80	13.595%	$234.9145	$234.91	$234.90	$234.90
Purchase #2	$104.75	5.618%	$110.6349	$110.63	$110.65	$110.60
Purchase #3	$111.25	4.442%	$116.1917	$116.19	$116.20	$116.20
Purchase #4	$107.51	3.297%	$111.0546	$111.05	$111.05	$111.10
Purchase #5	$107.80	3.135%	$111.1795	$111.18	$111.20	$111.20
Purchase #6	$156.46	7.711%	$168.5246	$168.52	$168.50	$168.50
Purchase #7	$212.51	7.552%	$228.5588	$228.56	$228.55	$228.60
7 purchase totals =	$1,007.08		$1,081.0586	$1,081.04	$1,081.05	$1,081.10