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	$250.43	5.319%	$263.7504	$263.75	$263.75	$263.80
Purchase #2	$18.52	11.317%	$20.6159	$20.62	$20.60	$20.60
Purchase #3	$241.87	9.505%	$264.8597	$264.86	$264.85	$264.90
Purchase #4	$135.76	8.369%	$147.1218	$147.12	$147.10	$147.10
Purchase #5	$217.83	9.386%	$238.2755	$238.28	$238.30	$238.30
Purchase #6	$52.78	13.216%	$59.7554	$59.76	$59.75	$59.80
Purchase #7	$33.34	8.113%	$36.0449	$36.04	$36.05	$36.00
7 purchase totals =	$950.53		$1,030.4236	$1,030.43	$1,030.40	$1,030.50