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	$193.64	6.131%	$205.5121	$205.51	$205.50	$205.50
Purchase #2	$216.28	12.419%	$243.1398	$243.14	$243.15	$243.10
Purchase #3	$245.56	7.510%	$264.0016	$264.00	$264.00	$264.00
Purchase #4	$41.70	13.808%	$47.4579	$47.46	$47.45	$47.50
Purchase #5	$47.38	10.196%	$52.2109	$52.21	$52.20	$52.20
Purchase #6	$165.73	9.574%	$181.597	$181.60	$181.60	$181.60
Purchase #7	$69.27	13.668%	$78.7378	$78.74	$78.75	$78.70
7 purchase totals =	$979.56		$1,072.6571	$1,072.66	$1,072.65	$1,072.60