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	$237.69	4.322%	$247.963	$247.96	$247.95	$248.00
Purchase #2	$241.35	11.734%	$269.67	$269.67	$269.65	$269.70
Purchase #3	$78.65	13.446%	$89.2253	$89.23	$89.25	$89.20
Purchase #4	$60.35	11.418%	$67.2408	$67.24	$67.25	$67.20
Purchase #5	$225.69	11.298%	$251.1885	$251.19	$251.20	$251.20
Purchase #6	$152.71	6.156%	$162.1108	$162.11	$162.10	$162.10
Purchase #7	$165.91	3.428%	$171.5974	$171.60	$171.60	$171.60
7 purchase totals =	$1,162.35		$1,258.9958	$1,259.00	$1,259.00	$1,259.00