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	$111.62	11.404%	$124.3491	$124.35	$124.35	$124.30
Purchase #2	$92.37	6.241%	$98.1348	$98.13	$98.15	$98.10
Purchase #3	$171.82	7.345%	$184.4402	$184.44	$184.45	$184.40
Purchase #4	$58.69	3.248%	$60.5963	$60.60	$60.60	$60.60
Purchase #5	$220.62	3.871%	$229.1602	$229.16	$229.15	$229.20
Purchase #6	$235.33	12.202%	$264.045	$264.05	$264.05	$264.00
Purchase #7	$50.48	12.581%	$56.8309	$56.83	$56.85	$56.80
7 purchase totals =	$940.93		$1,017.5565	$1,017.56	$1,017.60	$1,017.40