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	$222.44	8.828%	$242.077	$242.08	$242.10	$242.10
Purchase #2	$149.25	4.407%	$155.8274	$155.83	$155.85	$155.80
Purchase #3	$203.51	6.281%	$216.2925	$216.29	$216.30	$216.30
Purchase #4	$105.97	8.598%	$115.0813	$115.08	$115.10	$115.10
Purchase #5	$11.37	7.493%	$12.222	$12.22	$12.20	$12.20
Purchase #6	$41.25	5.581%	$43.5522	$43.55	$43.55	$43.60
Purchase #7	$82.54	8.320%	$89.4073	$89.41	$89.40	$89.40
7 purchase totals =	$816.33		$874.4597	$874.46	$874.50	$874.50