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	$79.82	11.231%	$88.7846	$88.78	$88.80	$88.80
Purchase #2	$117.69	9.227%	$128.5493	$128.55	$128.55	$128.50
Purchase #3	$126.64	12.857%	$142.9221	$142.92	$142.90	$142.90
Purchase #4	$108.92	4.196%	$113.4903	$113.49	$113.50	$113.50
Purchase #5	$178.77	5.445%	$188.504	$188.50	$188.50	$188.50
Purchase #6	$229.39	5.642%	$242.3322	$242.33	$242.35	$242.30
Purchase #7	$152.31	3.851%	$158.1755	$158.18	$158.20	$158.20
7 purchase totals =	$993.54		$1,062.7580	$1,062.75	$1,062.80	$1,062.70