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	$185.51	13.777%	$211.0677	$211.07	$211.05	$211.10
Purchase #2	$30.36	9.630%	$33.2837	$33.28	$33.30	$33.30
Purchase #3	$76.42	10.449%	$84.4051	$84.41	$84.40	$84.40
Purchase #4	$113.75	4.370%	$118.7209	$118.72	$118.70	$118.70
Purchase #5	$188.32	4.156%	$196.1466	$196.15	$196.15	$196.10
Purchase #6	$180.55	10.451%	$199.4193	$199.42	$199.40	$199.40
Purchase #7	$70.97	10.241%	$78.238	$78.24	$78.25	$78.20
7 purchase totals =	$845.88		$921.2813	$921.29	$921.25	$921.20