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	$211.49	12.686%	$238.3196	$238.32	$238.30	$238.30
Purchase #2	$246.90	11.401%	$275.0491	$275.05	$275.05	$275.00
Purchase #3	$59.52	4.384%	$62.1294	$62.13	$62.15	$62.10
Purchase #4	$87.87	10.787%	$97.3485	$97.35	$97.35	$97.30
Purchase #5	$43.57	9.444%	$47.6848	$47.68	$47.70	$47.70
Purchase #6	$244.46	10.658%	$270.5145	$270.51	$270.50	$270.50
Purchase #7	$23.72	3.197%	$24.4783	$24.48	$24.50	$24.50
7 purchase totals =	$917.53		$1,015.5242	$1,015.52	$1,015.55	$1,015.40