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	$179.74	4.401%	$187.6504	$187.65	$187.65	$187.70
Purchase #2	$178.89	5.401%	$188.5518	$188.55	$188.55	$188.60
Purchase #3	$84.28	3.742%	$87.4338	$87.43	$87.45	$87.40
Purchase #4	$92.28	6.736%	$98.496	$98.50	$98.50	$98.50
Purchase #5	$97.71	6.568%	$104.1276	$104.13	$104.15	$104.10
Purchase #6	$155.38	6.656%	$165.7221	$165.72	$165.70	$165.70
Purchase #7	$224.88	10.681%	$248.8994	$248.90	$248.90	$248.90
7 purchase totals =	$1,013.16		$1,080.8811	$1,080.88	$1,080.90	$1,080.90