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	$136.30	11.846%	$152.4461	$152.45	$152.45	$152.40
Purchase #2	$222.83	10.346%	$245.884	$245.88	$245.90	$245.90
Purchase #3	$145.36	3.255%	$150.0915	$150.09	$150.10	$150.10
Purchase #4	$220.37	11.360%	$245.404	$245.40	$245.40	$245.40
Purchase #5	$188.41	7.567%	$202.667	$202.67	$202.65	$202.70
Purchase #6	$41.40	3.505%	$42.8511	$42.85	$42.85	$42.90
Purchase #7	$222.90	4.548%	$233.0375	$233.04	$233.05	$233.00
7 purchase totals =	$1,177.57		$1,272.3812	$1,272.38	$1,272.40	$1,272.40