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	$104.97	7.304%	$112.637	$112.64	$112.65	$112.60
Purchase #2	$15.27	13.428%	$17.3205	$17.32	$17.30	$17.30
Purchase #3	$203.55	9.226%	$222.3295	$222.33	$222.35	$222.30
Purchase #4	$99.93	3.593%	$103.5205	$103.52	$103.50	$103.50
Purchase #5	$141.61	3.577%	$146.6754	$146.68	$146.70	$146.70
Purchase #6	$58.76	9.765%	$64.4979	$64.50	$64.50	$64.50
Purchase #7	$158.73	8.123%	$171.6236	$171.62	$171.60	$171.60
7 purchase totals =	$782.82		$838.6044	$838.61	$838.60	$838.50