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	$57.74	8.626%	$62.7207	$62.72	$62.70	$62.70
Purchase #2	$186.58	13.280%	$211.3578	$211.36	$211.35	$211.40
Purchase #3	$92.41	7.417%	$99.264	$99.26	$99.25	$99.30
Purchase #4	$120.64	8.359%	$130.7243	$130.72	$130.70	$130.70
Purchase #5	$73.90	4.345%	$77.111	$77.11	$77.10	$77.10
Purchase #6	$231.72	10.156%	$255.2535	$255.25	$255.25	$255.30
Purchase #7	$227.58	5.866%	$240.9298	$240.93	$240.95	$240.90
7 purchase totals =	$990.57		$1,077.3611	$1,077.35	$1,077.30	$1,077.40