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	$47.91	6.145%	$50.8541	$50.85	$50.85	$50.90
Purchase #2	$82.43	3.518%	$85.3299	$85.33	$85.35	$85.30
Purchase #3	$79.69	4.507%	$83.2816	$83.28	$83.30	$83.30
Purchase #4	$155.70	7.233%	$166.9618	$166.96	$166.95	$167.00
Purchase #5	$192.99	10.856%	$213.941	$213.94	$213.95	$213.90
Purchase #6	$61.68	4.157%	$64.244	$64.24	$64.25	$64.20
Purchase #7	$177.85	10.500%	$196.5243	$196.52	$196.50	$196.50
7 purchase totals =	$798.25		$861.1367	$861.12	$861.15	$861.10