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	$52.79	13.396%	$59.8617	$59.86	$59.85	$59.90
Purchase #2	$177.41	8.301%	$192.1368	$192.14	$192.15	$192.10
Purchase #3	$142.27	3.717%	$147.5582	$147.56	$147.55	$147.60
Purchase #4	$103.96	3.596%	$107.6984	$107.70	$107.70	$107.70
Purchase #5	$133.62	13.154%	$151.1964	$151.20	$151.20	$151.20
Purchase #6	$34.91	7.687%	$37.5935	$37.59	$37.60	$37.60
Purchase #7	$147.85	13.155%	$167.2997	$167.30	$167.30	$167.30
7 purchase totals =	$792.81		$863.3447	$863.35	$863.35	$863.40