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	$86.86	4.809%	$91.0371	$91.04	$91.05	$91.00
Purchase #2	$153.32	10.668%	$169.6762	$169.68	$169.70	$169.70
Purchase #3	$198.86	8.784%	$216.3279	$216.33	$216.35	$216.30
Purchase #4	$46.32	3.872%	$48.1135	$48.11	$48.10	$48.10
Purchase #5	$136.92	13.139%	$154.9099	$154.91	$154.90	$154.90
Purchase #6	$151.79	10.363%	$167.52	$167.52	$167.50	$167.50
Purchase #7	$164.40	4.115%	$171.1651	$171.17	$171.15	$171.20
7 purchase totals =	$938.47		$1,018.7497	$1,018.76	$1,018.75	$1,018.70