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	$234.87	4.335%	$245.0516	$245.05	$245.05	$245.10
Purchase #2	$236.78	12.304%	$265.9134	$265.91	$265.90	$265.90
Purchase #3	$234.97	11.565%	$262.1443	$262.14	$262.15	$262.10
Purchase #4	$51.46	3.568%	$53.2961	$53.30	$53.30	$53.30
Purchase #5	$83.62	9.501%	$91.5647	$91.56	$91.55	$91.60
Purchase #6	$241.64	3.702%	$250.5855	$250.59	$250.60	$250.60
Purchase #7	$18.94	7.204%	$20.3044	$20.30	$20.30	$20.30
7 purchase totals =	$1,102.28		$1,188.8600	$1,188.85	$1,188.85	$1,188.90