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	$58.56	6.358%	$62.2832	$62.28	$62.30	$62.30
Purchase #2	$106.46	12.661%	$119.9389	$119.94	$119.95	$119.90
Purchase #3	$88.63	5.174%	$93.2157	$93.22	$93.20	$93.20
Purchase #4	$63.92	12.497%	$71.9081	$71.91	$71.90	$71.90
Purchase #5	$50.41	6.794%	$53.8349	$53.83	$53.85	$53.80
Purchase #6	$53.72	6.816%	$57.3816	$57.38	$57.40	$57.40
Purchase #7	$153.33	4.636%	$160.4384	$160.44	$160.45	$160.40
7 purchase totals =	$575.03		$619.0008	$619.00	$619.05	$618.90