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	$196.34	9.461%	$214.9157	$214.92	$214.90	$214.90
Purchase #2	$165.69	3.774%	$171.9431	$171.94	$171.95	$171.90
Purchase #3	$51.97	5.507%	$54.832	$54.83	$54.85	$54.80
Purchase #4	$133.60	9.413%	$146.1758	$146.18	$146.20	$146.20
Purchase #5	$56.64	4.106%	$58.9656	$58.97	$58.95	$59.00
Purchase #6	$105.73	5.560%	$111.6086	$111.61	$111.60	$111.60
Purchase #7	$95.54	3.728%	$99.1017	$99.10	$99.10	$99.10
7 purchase totals =	$805.51		$857.5425	$857.55	$857.55	$857.50