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	$102.66	4.174%	$106.945	$106.95	$106.95	$106.90
Purchase #2	$160.60	5.721%	$169.7879	$169.79	$169.80	$169.80
Purchase #3	$76.54	10.345%	$84.4581	$84.46	$84.45	$84.50
Purchase #4	$56.97	9.134%	$62.1736	$62.17	$62.15	$62.20
Purchase #5	$104.64	7.287%	$112.2651	$112.27	$112.25	$112.30
Purchase #6	$181.32	8.391%	$196.5346	$196.53	$196.55	$196.50
Purchase #7	$19.79	6.621%	$21.1003	$21.10	$21.10	$21.10
7 purchase totals =	$702.52		$753.2646	$753.27	$753.25	$753.30