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	$88.75	13.439%	$100.6771	$100.68	$100.70	$100.70
Purchase #2	$191.98	4.171%	$199.9875	$199.99	$200.00	$200.00
Purchase #3	$172.47	8.810%	$187.6646	$187.66	$187.65	$187.70
Purchase #4	$250.98	5.290%	$264.2568	$264.26	$264.25	$264.30
Purchase #5	$245.80	5.754%	$259.9433	$259.94	$259.95	$259.90
Purchase #6	$11.89	3.272%	$12.279	$12.28	$12.30	$12.30
Purchase #7	$145.61	3.330%	$150.4588	$150.46	$150.45	$150.50
7 purchase totals =	$1,107.48		$1,175.2671	$1,175.27	$1,175.30	$1,175.40