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	$41.34	11.221%	$45.9788	$45.98	$46.00	$46.00
Purchase #2	$225.76	9.117%	$246.3425	$246.34	$246.35	$246.30
Purchase #3	$143.66	9.428%	$157.2043	$157.20	$157.20	$157.20
Purchase #4	$34.50	7.640%	$37.1358	$37.14	$37.15	$37.10
Purchase #5	$84.40	7.515%	$90.7427	$90.74	$90.75	$90.70
Purchase #6	$119.97	6.627%	$127.9204	$127.92	$127.90	$127.90
Purchase #7	$115.69	13.475%	$131.2792	$131.28	$131.30	$131.30
7 purchase totals =	$765.32		$836.6037	$836.60	$836.65	$836.50