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	$112.82	3.494%	$116.7619	$116.76	$116.75	$116.80
Purchase #2	$70.61	7.196%	$75.6911	$75.69	$75.70	$75.70
Purchase #3	$142.33	7.173%	$152.5393	$152.54	$152.55	$152.50
Purchase #4	$85.45	3.860%	$88.7484	$88.75	$88.75	$88.70
Purchase #5	$42.41	7.455%	$45.5717	$45.57	$45.55	$45.60
Purchase #6	$47.97	9.576%	$52.5636	$52.56	$52.55	$52.60
Purchase #7	$206.35	13.643%	$234.5023	$234.50	$234.50	$234.50
7 purchase totals =	$707.94		$766.3783	$766.37	$766.35	$766.40