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	$42.78	11.393%	$47.6539	$47.65	$47.65	$47.70
Purchase #2	$89.46	8.476%	$97.0426	$97.04	$97.05	$97.00
Purchase #3	$167.67	7.113%	$179.5964	$179.60	$179.60	$179.60
Purchase #4	$197.96	4.352%	$206.5752	$206.58	$206.60	$206.60
Purchase #5	$181.73	8.320%	$196.8499	$196.85	$196.85	$196.80
Purchase #6	$107.72	3.776%	$111.7875	$111.79	$111.80	$111.80
Purchase #7	$230.86	11.683%	$257.8314	$257.83	$257.85	$257.80
7 purchase totals =	$1,018.18		$1,097.3369	$1,097.34	$1,097.40	$1,097.30