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	$222.38	5.873%	$235.4404	$235.44	$235.45	$235.40
Purchase #2	$86.50	3.408%	$89.4479	$89.45	$89.45	$89.40
Purchase #3	$174.73	10.795%	$193.5921	$193.59	$193.60	$193.60
Purchase #4	$100.44	3.760%	$104.2165	$104.22	$104.20	$104.20
Purchase #5	$200.56	11.850%	$224.3264	$224.33	$224.35	$224.30
Purchase #6	$93.28	7.146%	$99.9458	$99.95	$99.95	$99.90
Purchase #7	$61.52	6.514%	$65.5274	$65.53	$65.55	$65.50
7 purchase totals =	$939.41		$1,012.4965	$1,012.51	$1,012.55	$1,012.30