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	$134.53	9.377%	$147.1449	$147.14	$147.15	$147.10
Purchase #2	$38.92	9.833%	$42.747	$42.75	$42.75	$42.70
Purchase #3	$171.85	11.532%	$191.6677	$191.67	$191.65	$191.70
Purchase #4	$112.46	12.558%	$126.5827	$126.58	$126.60	$126.60
Purchase #5	$133.63	12.433%	$150.2442	$150.24	$150.25	$150.20
Purchase #6	$98.83	12.418%	$111.1027	$111.10	$111.10	$111.10
Purchase #7	$50.87	10.581%	$56.2526	$56.25	$56.25	$56.30
7 purchase totals =	$741.09		$825.7418	$825.73	$825.75	$825.70