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	$170.55	5.204%	$179.4254	$179.43	$179.45	$179.40
Purchase #2	$194.84	13.745%	$221.6208	$221.62	$221.60	$221.60
Purchase #3	$200.43	5.463%	$211.3795	$211.38	$211.40	$211.40
Purchase #4	$85.91	11.814%	$96.0594	$96.06	$96.05	$96.10
Purchase #5	$109.45	6.363%	$116.4143	$116.41	$116.40	$116.40
Purchase #6	$102.31	8.843%	$111.3573	$111.36	$111.35	$111.40
Purchase #7	$106.33	7.354%	$114.1495	$114.15	$114.15	$114.10
7 purchase totals =	$969.82		$1,050.4062	$1,050.41	$1,050.40	$1,050.40