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	$178.76	3.524%	$185.0595	$185.06	$185.05	$185.10
Purchase #2	$69.58	13.270%	$78.8133	$78.81	$78.80	$78.80
Purchase #3	$165.93	3.816%	$172.2619	$172.26	$172.25	$172.30
Purchase #4	$199.61	7.341%	$214.2634	$214.26	$214.25	$214.30
Purchase #5	$210.47	6.102%	$223.3129	$223.31	$223.30	$223.30
Purchase #6	$237.92	3.342%	$245.8713	$245.87	$245.85	$245.90
Purchase #7	$86.85	7.840%	$93.659	$93.66	$93.65	$93.70
7 purchase totals =	$1,149.12		$1,213.2413	$1,213.23	$1,213.15	$1,213.40