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	$40.63	12.789%	$45.8262	$45.83	$45.85	$45.80
Purchase #2	$142.84	5.501%	$150.6976	$150.70	$150.70	$150.70
Purchase #3	$89.75	12.552%	$101.0154	$101.02	$101.00	$101.00
Purchase #4	$168.40	8.612%	$182.9026	$182.90	$182.90	$182.90
Purchase #5	$248.49	5.825%	$262.9645	$262.96	$262.95	$263.00
Purchase #6	$147.29	11.705%	$164.5303	$164.53	$164.55	$164.50
Purchase #7	$174.72	6.341%	$185.799	$185.80	$185.80	$185.80
7 purchase totals =	$1,012.12		$1,093.7356	$1,093.74	$1,093.75	$1,093.70