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	$106.80	3.377%	$110.4066	$110.41	$110.40	$110.40
Purchase #2	$57.93	3.214%	$59.7919	$59.79	$59.80	$59.80
Purchase #3	$114.34	10.792%	$126.6796	$126.68	$126.70	$126.70
Purchase #4	$145.42	9.513%	$159.2538	$159.25	$159.25	$159.30
Purchase #5	$229.50	11.449%	$255.7755	$255.78	$255.80	$255.80
Purchase #6	$93.78	6.702%	$100.0651	$100.07	$100.05	$100.10
Purchase #7	$224.25	9.299%	$245.103	$245.10	$245.10	$245.10
7 purchase totals =	$972.02		$1,057.0755	$1,057.08	$1,057.10	$1,057.20