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	$52.32	5.405%	$55.1479	$55.15	$55.15	$55.10
Purchase #2	$64.93	3.844%	$67.4259	$67.43	$67.45	$67.40
Purchase #3	$73.70	5.695%	$77.8972	$77.90	$77.90	$77.90
Purchase #4	$127.33	13.446%	$144.4508	$144.45	$144.45	$144.50
Purchase #5	$140.32	8.292%	$151.9553	$151.96	$151.95	$152.00
Purchase #6	$89.96	9.201%	$98.2372	$98.24	$98.25	$98.20
Purchase #7	$23.34	5.240%	$24.563	$24.56	$24.55	$24.60
7 purchase totals =	$571.90		$619.6773	$619.69	$619.70	$619.70