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	$218.75	12.230%	$245.5031	$245.50	$245.50	$245.50
Purchase #2	$79.63	12.343%	$89.4587	$89.46	$89.45	$89.50
Purchase #3	$145.30	11.567%	$162.1069	$162.11	$162.10	$162.10
Purchase #4	$17.56	4.797%	$18.4024	$18.40	$18.40	$18.40
Purchase #5	$187.35	13.570%	$212.7734	$212.77	$212.75	$212.80
Purchase #6	$152.74	5.629%	$161.3377	$161.34	$161.35	$161.30
Purchase #7	$245.52	8.699%	$266.8778	$266.88	$266.90	$266.90
7 purchase totals =	$1,046.85		$1,156.4600	$1,156.46	$1,156.45	$1,156.50