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	$248.34	9.224%	$271.2469	$271.25	$271.25	$271.20
Purchase #2	$88.59	9.786%	$97.2594	$97.26	$97.25	$97.30
Purchase #3	$81.68	10.471%	$90.2327	$90.23	$90.25	$90.20
Purchase #4	$242.90	10.172%	$267.6078	$267.61	$267.60	$267.60
Purchase #5	$174.65	8.646%	$189.7502	$189.75	$189.75	$189.80
Purchase #6	$38.92	9.486%	$42.612	$42.61	$42.60	$42.60
Purchase #7	$121.74	12.230%	$136.6288	$136.63	$136.65	$136.60
7 purchase totals =	$996.82		$1,095.3378	$1,095.34	$1,095.35	$1,095.30