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	$228.90	3.183%	$236.1859	$236.19	$236.20	$236.20
Purchase #2	$38.66	10.442%	$42.6969	$42.70	$42.70	$42.70
Purchase #3	$55.65	6.283%	$59.1465	$59.15	$59.15	$59.10
Purchase #4	$136.55	12.151%	$153.1422	$153.14	$153.15	$153.10
Purchase #5	$209.50	6.496%	$223.1091	$223.11	$223.10	$223.10
Purchase #6	$227.38	12.213%	$255.1499	$255.15	$255.15	$255.10
Purchase #7	$248.26	10.303%	$273.8382	$273.84	$273.85	$273.80
7 purchase totals =	$1,144.90		$1,243.2687	$1,243.28	$1,243.30	$1,243.10