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	$26.86	8.555%	$29.1579	$29.16	$29.15	$29.20
Purchase #2	$21.26	12.441%	$23.905	$23.91	$23.90	$23.90
Purchase #3	$159.57	12.370%	$179.3088	$179.31	$179.30	$179.30
Purchase #4	$182.61	7.527%	$196.3551	$196.36	$196.35	$196.40
Purchase #5	$142.41	10.125%	$156.829	$156.83	$156.85	$156.80
Purchase #6	$235.72	4.137%	$245.4717	$245.47	$245.45	$245.50
Purchase #7	$172.61	13.637%	$196.1488	$196.15	$196.15	$196.10
7 purchase totals =	$941.04		$1,027.1763	$1,027.19	$1,027.15	$1,027.20