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	$32.75	13.692%	$37.2341	$37.23	$37.25	$37.20
Purchase #2	$92.35	6.559%	$98.4072	$98.41	$98.40	$98.40
Purchase #3	$60.81	12.231%	$68.2477	$68.25	$68.25	$68.20
Purchase #4	$57.35	3.134%	$59.1473	$59.15	$59.15	$59.10
Purchase #5	$220.69	11.202%	$245.4117	$245.41	$245.40	$245.40
Purchase #6	$207.35	12.666%	$233.613	$233.61	$233.60	$233.60
Purchase #7	$149.59	6.157%	$158.8003	$158.80	$158.80	$158.80
7 purchase totals =	$820.89		$900.8613	$900.86	$900.85	$900.70