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	$194.94	7.401%	$209.3675	$209.37	$209.35	$209.40
Purchase #2	$173.39	7.663%	$186.6769	$186.68	$186.70	$186.70
Purchase #3	$150.51	3.463%	$155.7222	$155.72	$155.70	$155.70
Purchase #4	$121.75	3.614%	$126.15	$126.15	$126.15	$126.20
Purchase #5	$234.89	6.722%	$250.6793	$250.68	$250.70	$250.70
Purchase #6	$63.37	3.729%	$65.7331	$65.73	$65.75	$65.70
Purchase #7	$111.31	5.587%	$117.5289	$117.53	$117.55	$117.50
7 purchase totals =	$1,050.16		$1,111.8579	$1,111.86	$1,111.90	$1,111.90