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	$121.71	7.190%	$130.4609	$130.46	$130.45	$130.50
Purchase #2	$85.95	10.578%	$95.0418	$95.04	$95.05	$95.00
Purchase #3	$28.63	11.415%	$31.8981	$31.90	$31.90	$31.90
Purchase #4	$52.37	13.144%	$59.2535	$59.25	$59.25	$59.30
Purchase #5	$107.70	6.104%	$114.274	$114.27	$114.25	$114.30
Purchase #6	$174.72	9.202%	$190.7977	$190.80	$190.80	$190.80
Purchase #7	$31.43	3.110%	$32.4075	$32.41	$32.40	$32.40
7 purchase totals =	$602.51		$654.1335	$654.13	$654.10	$654.20