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	$72.73	5.321%	$76.6	$76.60	$76.60	$76.60
Purchase #2	$111.62	12.403%	$125.4642	$125.46	$125.45	$125.50
Purchase #3	$46.97	13.489%	$53.3058	$53.31	$53.30	$53.30
Purchase #4	$192.98	3.798%	$200.3094	$200.31	$200.30	$200.30
Purchase #5	$64.87	4.179%	$67.5809	$67.58	$67.60	$67.60
Purchase #6	$156.59	5.773%	$165.6299	$165.63	$165.65	$165.60
Purchase #7	$151.25	9.166%	$165.1136	$165.11	$165.10	$165.10
7 purchase totals =	$797.01		$854.0038	$854.00	$854.00	$854.00