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	$172.66	7.254%	$185.1848	$185.18	$185.20	$185.20
Purchase #2	$103.49	7.475%	$111.2259	$111.23	$111.25	$111.20
Purchase #3	$125.60	4.831%	$131.6677	$131.67	$131.65	$131.70
Purchase #4	$207.89	3.794%	$215.7773	$215.78	$215.80	$215.80
Purchase #5	$39.63	9.293%	$43.3128	$43.31	$43.30	$43.30
Purchase #6	$150.41	5.814%	$159.1548	$159.15	$159.15	$159.20
Purchase #7	$165.63	11.521%	$184.7122	$184.71	$184.70	$184.70
7 purchase totals =	$965.31		$1,031.0355	$1,031.03	$1,031.05	$1,031.10