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	$51.65	3.479%	$53.4469	$53.45	$53.45	$53.40
Purchase #2	$14.66	6.860%	$15.6657	$15.67	$15.65	$15.70
Purchase #3	$31.25	5.459%	$32.9559	$32.96	$32.95	$33.00
Purchase #4	$184.72	6.128%	$196.0396	$196.04	$196.05	$196.00
Purchase #5	$233.86	4.401%	$244.1522	$244.15	$244.15	$244.20
Purchase #6	$215.39	11.317%	$239.7657	$239.77	$239.75	$239.80
Purchase #7	$71.98	12.345%	$80.8659	$80.87	$80.85	$80.90
7 purchase totals =	$803.51		$862.8919	$862.91	$862.85	$863.00