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	$183.79	7.808%	$198.1403	$198.14	$198.15	$198.10
Purchase #2	$70.32	11.591%	$78.4708	$78.47	$78.45	$78.50
Purchase #3	$89.26	10.596%	$98.718	$98.72	$98.70	$98.70
Purchase #4	$47.67	4.699%	$49.91	$49.91	$49.90	$49.90
Purchase #5	$78.73	4.198%	$82.0351	$82.04	$82.05	$82.00
Purchase #6	$182.91	9.502%	$200.2901	$200.29	$200.30	$200.30
Purchase #7	$197.41	10.649%	$218.4322	$218.43	$218.45	$218.40
7 purchase totals =	$850.09		$925.9965	$926.00	$926.00	$925.90