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	$114.87	13.654%	$130.5543	$130.55	$130.55	$130.60
Purchase #2	$57.47	12.381%	$64.5854	$64.59	$64.60	$64.60
Purchase #3	$7.70	5.639%	$8.1342	$8.13	$8.15	$8.10
Purchase #4	$76.59	11.279%	$85.2286	$85.23	$85.25	$85.20
Purchase #5	$57.77	4.296%	$60.2518	$60.25	$60.25	$60.30
Purchase #6	$150.61	6.642%	$160.6135	$160.61	$160.60	$160.60
Purchase #7	$42.30	13.243%	$47.9018	$47.90	$47.90	$47.90
7 purchase totals =	$507.31		$557.2696	$557.26	$557.30	$557.30