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	$147.35	8.273%	$159.5403	$159.54	$159.55	$159.50
Purchase #2	$90.62	11.279%	$100.841	$100.84	$100.85	$100.80
Purchase #3	$31.49	4.873%	$33.0245	$33.02	$33.00	$33.00
Purchase #4	$127.99	11.444%	$142.6372	$142.64	$142.65	$142.60
Purchase #5	$150.31	10.459%	$166.0309	$166.03	$166.05	$166.00
Purchase #6	$232.40	7.645%	$250.167	$250.17	$250.15	$250.20
Purchase #7	$181.89	12.280%	$204.2261	$204.23	$204.25	$204.20
7 purchase totals =	$962.05		$1,056.4670	$1,056.47	$1,056.50	$1,056.30