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	$164.85	8.776%	$179.3172	$179.32	$179.30	$179.30
Purchase #2	$58.80	6.517%	$62.632	$62.63	$62.65	$62.60
Purchase #3	$89.67	3.511%	$92.8183	$92.82	$92.80	$92.80
Purchase #4	$149.59	7.498%	$160.8063	$160.81	$160.80	$160.80
Purchase #5	$143.88	5.214%	$151.3819	$151.38	$151.40	$151.40
Purchase #6	$101.70	9.469%	$111.33	$111.33	$111.35	$111.30
Purchase #7	$240.36	5.824%	$254.3586	$254.36	$254.35	$254.40
7 purchase totals =	$948.85		$1,012.6443	$1,012.65	$1,012.65	$1,012.60