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	$196.99	13.265%	$223.1207	$223.12	$223.10	$223.10
Purchase #2	$162.41	8.441%	$176.119	$176.12	$176.10	$176.10
Purchase #3	$136.50	12.407%	$153.4356	$153.44	$153.45	$153.40
Purchase #4	$243.41	8.687%	$264.555	$264.56	$264.55	$264.60
Purchase #5	$223.76	9.389%	$244.7688	$244.77	$244.75	$244.80
Purchase #6	$45.28	10.565%	$50.0638	$50.06	$50.05	$50.10
Purchase #7	$137.85	10.611%	$152.4773	$152.48	$152.50	$152.50
7 purchase totals =	$1,146.20		$1,264.5402	$1,264.55	$1,264.50	$1,264.60