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	$188.41	3.667%	$195.319	$195.32	$195.30	$195.30
Purchase #2	$37.84	13.336%	$42.8863	$42.89	$42.90	$42.90
Purchase #3	$26.26	7.607%	$28.2576	$28.26	$28.25	$28.30
Purchase #4	$193.68	4.170%	$201.7565	$201.76	$201.75	$201.80
Purchase #5	$73.70	13.379%	$83.5603	$83.56	$83.55	$83.60
Purchase #6	$109.53	6.669%	$116.8346	$116.83	$116.85	$116.80
Purchase #7	$70.84	11.360%	$78.8874	$78.89	$78.90	$78.90
7 purchase totals =	$700.26		$747.5017	$747.51	$747.50	$747.60