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	$35.94	4.589%	$37.5893	$37.59	$37.60	$37.60
Purchase #2	$11.79	6.530%	$12.5599	$12.56	$12.55	$12.60
Purchase #3	$186.46	5.288%	$196.32	$196.32	$196.30	$196.30
Purchase #4	$179.85	5.723%	$190.1428	$190.14	$190.15	$190.10
Purchase #5	$173.72	8.303%	$188.144	$188.14	$188.15	$188.10
Purchase #6	$87.74	4.364%	$91.569	$91.57	$91.55	$91.60
Purchase #7	$73.61	6.450%	$78.3578	$78.36	$78.35	$78.40
7 purchase totals =	$749.11		$794.6828	$794.68	$794.65	$794.70