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	$194.52	7.627%	$209.356	$209.36	$209.35	$209.40
Purchase #2	$98.91	12.520%	$111.2935	$111.29	$111.30	$111.30
Purchase #3	$107.34	5.584%	$113.3339	$113.33	$113.35	$113.30
Purchase #4	$25.28	7.595%	$27.2	$27.20	$27.20	$27.20
Purchase #5	$75.38	6.617%	$80.3679	$80.37	$80.35	$80.40
Purchase #6	$239.51	3.373%	$247.5887	$247.59	$247.60	$247.60
Purchase #7	$29.95	5.700%	$31.6572	$31.66	$31.65	$31.70
7 purchase totals =	$770.89		$820.7972	$820.80	$820.80	$820.90