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	$40.73	10.559%	$45.0307	$45.03	$45.05	$45.00
Purchase #2	$75.29	3.816%	$78.1631	$78.16	$78.15	$78.20
Purchase #3	$55.48	6.253%	$58.9492	$58.95	$58.95	$58.90
Purchase #4	$62.46	13.140%	$70.6672	$70.67	$70.65	$70.70
Purchase #5	$174.62	9.424%	$191.0762	$191.08	$191.10	$191.10
Purchase #6	$48.90	7.470%	$52.5528	$52.55	$52.55	$52.60
Purchase #7	$69.93	5.609%	$73.8524	$73.85	$73.85	$73.90
7 purchase totals =	$527.41		$570.2916	$570.29	$570.30	$570.40