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	$126.30	3.578%	$130.819	$130.82	$130.80	$130.80
Purchase #2	$142.73	6.482%	$151.9818	$151.98	$152.00	$152.00
Purchase #3	$77.42	8.330%	$83.8691	$83.87	$83.85	$83.90
Purchase #4	$165.91	6.266%	$176.3059	$176.31	$176.30	$176.30
Purchase #5	$155.69	7.833%	$167.8852	$167.89	$167.90	$167.90
Purchase #6	$173.49	9.565%	$190.0843	$190.08	$190.10	$190.10
Purchase #7	$229.95	13.814%	$261.7153	$261.72	$261.70	$261.70
7 purchase totals =	$1,071.49		$1,162.6606	$1,162.67	$1,162.65	$1,162.70