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	$42.56	9.117%	$46.4402	$46.44	$46.45	$46.40
Purchase #2	$94.69	13.535%	$107.5063	$107.51	$107.50	$107.50
Purchase #3	$76.70	5.103%	$80.614	$80.61	$80.60	$80.60
Purchase #4	$190.30	3.281%	$196.5437	$196.54	$196.55	$196.50
Purchase #5	$93.89	4.618%	$98.2258	$98.23	$98.25	$98.20
Purchase #6	$170.72	10.557%	$188.7429	$188.74	$188.75	$188.70
Purchase #7	$97.40	3.193%	$100.51	$100.51	$100.50	$100.50
7 purchase totals =	$766.26		$818.5829	$818.58	$818.60	$818.40