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	$147.58	4.195%	$153.771	$153.77	$153.75	$153.80
Purchase #2	$166.49	7.536%	$179.0367	$179.04	$179.05	$179.00
Purchase #3	$34.65	13.154%	$39.2079	$39.21	$39.20	$39.20
Purchase #4	$208.62	8.773%	$226.9222	$226.92	$226.90	$226.90
Purchase #5	$188.54	6.108%	$200.056	$200.06	$200.05	$200.10
Purchase #6	$81.95	10.222%	$90.3269	$90.33	$90.35	$90.30
Purchase #7	$248.47	13.627%	$282.329	$282.33	$282.35	$282.30
7 purchase totals =	$1,076.30		$1,171.6497	$1,171.66	$1,171.65	$1,171.60