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	$188.56	4.409%	$196.8736	$196.87	$196.85	$196.90
Purchase #2	$189.49	12.360%	$212.911	$212.91	$212.90	$212.90
Purchase #3	$168.54	13.233%	$190.8429	$190.84	$190.85	$190.80
Purchase #4	$46.85	3.567%	$48.5211	$48.52	$48.50	$48.50
Purchase #5	$209.57	12.224%	$235.1878	$235.19	$235.20	$235.20
Purchase #6	$11.51	12.290%	$12.9246	$12.92	$12.90	$12.90
Purchase #7	$127.79	13.297%	$144.7822	$144.78	$144.80	$144.80
7 purchase totals =	$942.31		$1,042.0432	$1,042.03	$1,042.00	$1,042.00