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	$148.61	7.657%	$159.9891	$159.99	$160.00	$160.00
Purchase #2	$30.49	5.867%	$32.2788	$32.28	$32.30	$32.30
Purchase #3	$42.72	11.397%	$47.5888	$47.59	$47.60	$47.60
Purchase #4	$250.54	12.206%	$281.1209	$281.12	$281.10	$281.10
Purchase #5	$216.31	13.525%	$245.5659	$245.57	$245.55	$245.60
Purchase #6	$64.73	3.641%	$67.0868	$67.09	$67.10	$67.10
Purchase #7	$188.27	4.453%	$196.6537	$196.65	$196.65	$196.70
7 purchase totals =	$941.67		$1,030.2840	$1,030.29	$1,030.30	$1,030.40