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	$144.63	4.646%	$151.3495	$151.35	$151.35	$151.30
Purchase #2	$193.36	10.362%	$213.396	$213.40	$213.40	$213.40
Purchase #3	$97.53	12.634%	$109.8519	$109.85	$109.85	$109.90
Purchase #4	$169.58	9.294%	$185.3408	$185.34	$185.35	$185.30
Purchase #5	$48.89	12.404%	$54.9543	$54.95	$54.95	$55.00
Purchase #6	$246.95	12.296%	$277.315	$277.32	$277.30	$277.30
Purchase #7	$39.34	6.678%	$41.9671	$41.97	$41.95	$42.00
7 purchase totals =	$940.28		$1,034.1746	$1,034.18	$1,034.15	$1,034.20