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	$154.83	7.163%	$165.9205	$165.92	$165.90	$165.90
Purchase #2	$25.64	3.410%	$26.5143	$26.51	$26.50	$26.50
Purchase #3	$159.80	12.315%	$179.4794	$179.48	$179.50	$179.50
Purchase #4	$215.31	4.775%	$225.5911	$225.59	$225.60	$225.60
Purchase #5	$198.77	7.104%	$212.8906	$212.89	$212.90	$212.90
Purchase #6	$152.91	7.794%	$164.8278	$164.83	$164.85	$164.80
Purchase #7	$213.40	3.819%	$221.5497	$221.55	$221.55	$221.50
7 purchase totals =	$1,120.66		$1,196.7734	$1,196.77	$1,196.80	$1,196.70