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	$155.28	6.469%	$165.3251	$165.33	$165.35	$165.30
Purchase #2	$104.29	6.511%	$111.0803	$111.08	$111.10	$111.10
Purchase #3	$121.58	5.614%	$128.4055	$128.41	$128.40	$128.40
Purchase #4	$215.67	7.802%	$232.4966	$232.50	$232.50	$232.50
Purchase #5	$127.47	7.830%	$137.4509	$137.45	$137.45	$137.50
Purchase #6	$245.90	11.168%	$273.3621	$273.36	$273.35	$273.40
Purchase #7	$201.53	13.168%	$228.0675	$228.07	$228.05	$228.10
7 purchase totals =	$1,171.72		$1,276.1880	$1,276.20	$1,276.20	$1,276.30