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	$55.76	5.538%	$58.848	$58.85	$58.85	$58.80
Purchase #2	$166.43	10.122%	$183.276	$183.28	$183.30	$183.30
Purchase #3	$140.44	3.872%	$145.8778	$145.88	$145.90	$145.90
Purchase #4	$244.30	4.565%	$255.4523	$255.45	$255.45	$255.50
Purchase #5	$50.32	8.360%	$54.5268	$54.53	$54.55	$54.50
Purchase #6	$45.26	4.534%	$47.3121	$47.31	$47.30	$47.30
Purchase #7	$250.42	10.232%	$276.043	$276.04	$276.05	$276.00
7 purchase totals =	$952.93		$1,021.3360	$1,021.34	$1,021.40	$1,021.30