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	$247.64	7.343%	$265.8242	$265.82	$265.80	$265.80
Purchase #2	$245.63	12.337%	$275.9334	$275.93	$275.95	$275.90
Purchase #3	$128.41	10.183%	$141.486	$141.49	$141.50	$141.50
Purchase #4	$34.33	11.790%	$38.3775	$38.38	$38.40	$38.40
Purchase #5	$121.58	3.308%	$125.6019	$125.60	$125.60	$125.60
Purchase #6	$82.38	9.629%	$90.3124	$90.31	$90.30	$90.30
Purchase #7	$143.58	3.817%	$149.0604	$149.06	$149.05	$149.10
7 purchase totals =	$1,003.55		$1,086.5958	$1,086.59	$1,086.60	$1,086.60