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	$86.34	12.804%	$97.395	$97.40	$97.40	$97.40
Purchase #2	$249.38	13.742%	$283.6498	$283.65	$283.65	$283.60
Purchase #3	$219.84	4.303%	$229.2997	$229.30	$229.30	$229.30
Purchase #4	$156.75	5.301%	$165.0593	$165.06	$165.05	$165.10
Purchase #5	$37.29	13.273%	$42.2395	$42.24	$42.25	$42.20
Purchase #6	$134.76	6.338%	$143.3011	$143.30	$143.30	$143.30
Purchase #7	$39.62	7.582%	$42.624	$42.62	$42.60	$42.60
7 purchase totals =	$923.98		$1,003.5684	$1,003.57	$1,003.55	$1,003.50