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	$234.48	3.260%	$242.124	$242.12	$242.10	$242.10
Purchase #2	$243.91	13.496%	$276.8281	$276.83	$276.85	$276.80
Purchase #3	$184.89	3.528%	$191.4129	$191.41	$191.40	$191.40
Purchase #4	$80.46	12.556%	$90.5626	$90.56	$90.55	$90.60
Purchase #5	$54.52	4.849%	$57.1637	$57.16	$57.15	$57.20
Purchase #6	$42.89	6.707%	$45.7666	$45.77	$45.75	$45.80
Purchase #7	$223.34	3.457%	$231.0609	$231.06	$231.05	$231.10
7 purchase totals =	$1,064.49		$1,134.9188	$1,134.91	$1,134.85	$1,135.00