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	$125.40	11.267%	$139.5288	$139.53	$139.55	$139.50
Purchase #2	$144.28	5.637%	$152.4131	$152.41	$152.40	$152.40
Purchase #3	$65.92	9.332%	$72.0717	$72.07	$72.05	$72.10
Purchase #4	$42.60	9.369%	$46.5912	$46.59	$46.60	$46.60
Purchase #5	$218.80	11.434%	$243.8176	$243.82	$243.80	$243.80
Purchase #6	$163.85	6.478%	$174.4642	$174.46	$174.45	$174.50
Purchase #7	$172.66	5.682%	$182.4705	$182.47	$182.45	$182.50
7 purchase totals =	$933.51		$1,011.3571	$1,011.35	$1,011.30	$1,011.40