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	$40.38	10.540%	$44.6361	$44.64	$44.65	$44.60
Purchase #2	$250.52	9.849%	$275.1937	$275.19	$275.20	$275.20
Purchase #3	$58.57	5.631%	$61.8681	$61.87	$61.85	$61.90
Purchase #4	$173.42	9.676%	$190.2001	$190.20	$190.20	$190.20
Purchase #5	$224.88	7.867%	$242.5713	$242.57	$242.55	$242.60
Purchase #6	$222.65	3.589%	$230.6409	$230.64	$230.65	$230.60
Purchase #7	$130.27	11.872%	$145.7357	$145.74	$145.75	$145.70
7 purchase totals =	$1,100.69		$1,190.8459	$1,190.85	$1,190.85	$1,190.80