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	$144.64	6.870%	$154.5768	$154.58	$154.60	$154.60
Purchase #2	$143.30	4.643%	$149.9534	$149.95	$149.95	$150.00
Purchase #3	$39.90	13.343%	$45.2239	$45.22	$45.20	$45.20
Purchase #4	$192.84	11.874%	$215.7378	$215.74	$215.75	$215.70
Purchase #5	$79.47	12.331%	$89.2694	$89.27	$89.25	$89.30
Purchase #6	$194.90	5.648%	$205.908	$205.91	$205.90	$205.90
Purchase #7	$206.33	13.563%	$234.3145	$234.31	$234.30	$234.30
7 purchase totals =	$1,001.38		$1,094.9838	$1,094.98	$1,094.95	$1,095.00