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	$76.62	10.193%	$84.4299	$84.43	$84.45	$84.40
Purchase #2	$83.57	6.650%	$89.1274	$89.13	$89.15	$89.10
Purchase #3	$195.97	13.367%	$222.1653	$222.17	$222.15	$222.20
Purchase #4	$159.79	9.411%	$174.8278	$174.83	$174.85	$174.80
Purchase #5	$128.34	4.679%	$134.345	$134.35	$134.35	$134.30
Purchase #6	$52.91	12.619%	$59.5867	$59.59	$59.60	$59.60
Purchase #7	$40.44	8.501%	$43.8778	$43.88	$43.90	$43.90
7 purchase totals =	$737.64		$808.3599	$808.38	$808.45	$808.30