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	$246.51	8.321%	$267.0221	$267.02	$267.00	$267.00
Purchase #2	$57.47	3.236%	$59.3297	$59.33	$59.35	$59.30
Purchase #3	$245.25	11.422%	$273.2625	$273.26	$273.25	$273.30
Purchase #4	$193.76	3.590%	$200.716	$200.72	$200.70	$200.70
Purchase #5	$46.85	13.800%	$53.3153	$53.32	$53.30	$53.30
Purchase #6	$88.48	13.510%	$100.4336	$100.43	$100.45	$100.40
Purchase #7	$82.33	7.713%	$88.6801	$88.68	$88.70	$88.70
7 purchase totals =	$960.65		$1,042.7593	$1,042.76	$1,042.75	$1,042.70