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	$60.62	11.467%	$67.5713	$67.57	$67.55	$67.60
Purchase #2	$213.32	3.851%	$221.535	$221.54	$221.55	$221.50
Purchase #3	$57.31	9.499%	$62.7539	$62.75	$62.75	$62.80
Purchase #4	$81.39	11.399%	$90.6676	$90.67	$90.65	$90.70
Purchase #5	$13.83	10.222%	$15.2437	$15.24	$15.25	$15.20
Purchase #6	$134.43	12.113%	$150.7135	$150.71	$150.70	$150.70
Purchase #7	$207.37	4.424%	$216.544	$216.54	$216.55	$216.50
7 purchase totals =	$768.27		$825.0290	$825.02	$825.00	$825.00