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	$43.70	3.802%	$45.3615	$45.36	$45.35	$45.40
Purchase #2	$187.53	11.292%	$208.7059	$208.71	$208.70	$208.70
Purchase #3	$213.81	7.477%	$229.7966	$229.80	$229.80	$229.80
Purchase #4	$222.30	7.328%	$238.5901	$238.59	$238.60	$238.60
Purchase #5	$237.69	5.368%	$250.4492	$250.45	$250.45	$250.40
Purchase #6	$116.68	9.198%	$127.4122	$127.41	$127.40	$127.40
Purchase #7	$26.34	13.639%	$29.9325	$29.93	$29.95	$29.90
7 purchase totals =	$1,048.05		$1,130.2480	$1,130.25	$1,130.25	$1,130.20