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	$156.31	7.541%	$168.0973	$168.10	$168.10	$168.10
Purchase #2	$234.84	3.215%	$242.3901	$242.39	$242.40	$242.40
Purchase #3	$206.37	10.544%	$228.1297	$228.13	$228.15	$228.10
Purchase #4	$127.39	13.810%	$144.9826	$144.98	$145.00	$145.00
Purchase #5	$120.96	5.179%	$127.2245	$127.22	$127.20	$127.20
Purchase #6	$50.71	4.545%	$53.0148	$53.01	$53.00	$53.00
Purchase #7	$130.46	7.530%	$140.2836	$140.28	$140.30	$140.30
7 purchase totals =	$1,027.04		$1,104.1226	$1,104.11	$1,104.15	$1,104.10