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	$232.25	13.401%	$263.3738	$263.37	$263.35	$263.40
Purchase #2	$85.61	12.540%	$96.3455	$96.35	$96.35	$96.30
Purchase #3	$77.48	13.860%	$88.2187	$88.22	$88.20	$88.20
Purchase #4	$9.51	12.225%	$10.6726	$10.67	$10.65	$10.70
Purchase #5	$147.96	7.818%	$159.5275	$159.53	$159.55	$159.50
Purchase #6	$52.98	12.796%	$59.7593	$59.76	$59.75	$59.80
Purchase #7	$114.88	11.224%	$127.7741	$127.77	$127.75	$127.80
7 purchase totals =	$720.67		$805.6715	$805.67	$805.60	$805.70