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	$50.52	4.368%	$52.7267	$52.73	$52.75	$52.70
Purchase #2	$42.56	8.560%	$46.2031	$46.20	$46.20	$46.20
Purchase #3	$49.32	9.449%	$53.9802	$53.98	$54.00	$54.00
Purchase #4	$104.70	12.530%	$117.8189	$117.82	$117.80	$117.80
Purchase #5	$68.72	3.780%	$71.3176	$71.32	$71.30	$71.30
Purchase #6	$36.96	6.510%	$39.3661	$39.37	$39.35	$39.40
Purchase #7	$206.57	7.841%	$222.7672	$222.77	$222.75	$222.80
7 purchase totals =	$559.35		$604.1798	$604.19	$604.15	$604.20