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	$101.47	9.748%	$111.3613	$111.36	$111.35	$111.40
Purchase #2	$106.55	11.749%	$119.0686	$119.07	$119.05	$119.10
Purchase #3	$190.93	10.654%	$211.2717	$211.27	$211.25	$211.30
Purchase #4	$218.87	4.743%	$229.251	$229.25	$229.25	$229.30
Purchase #5	$244.31	11.670%	$272.821	$272.82	$272.80	$272.80
Purchase #6	$232.86	7.297%	$249.8518	$249.85	$249.85	$249.90
Purchase #7	$233.31	4.392%	$243.557	$243.56	$243.55	$243.60
7 purchase totals =	$1,328.30		$1,437.1824	$1,437.18	$1,437.10	$1,437.40