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	$174.28	4.228%	$181.6486	$181.65	$181.65	$181.60
Purchase #2	$61.66	6.660%	$65.7666	$65.77	$65.75	$65.80
Purchase #3	$36.35	4.305%	$37.9149	$37.91	$37.90	$37.90
Purchase #4	$88.60	7.414%	$95.1688	$95.17	$95.15	$95.20
Purchase #5	$12.46	10.112%	$13.72	$13.72	$13.70	$13.70
Purchase #6	$17.88	11.648%	$19.9627	$19.96	$19.95	$20.00
Purchase #7	$65.29	13.186%	$73.8991	$73.90	$73.90	$73.90
7 purchase totals =	$456.52		$488.0807	$488.08	$488.00	$488.10