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	$175.71	7.172%	$188.3119	$188.31	$188.30	$188.30
Purchase #2	$48.96	6.768%	$52.2736	$52.27	$52.25	$52.30
Purchase #3	$194.54	12.300%	$218.4684	$218.47	$218.45	$218.50
Purchase #4	$83.54	7.342%	$89.6735	$89.67	$89.65	$89.70
Purchase #5	$34.82	13.317%	$39.457	$39.46	$39.45	$39.50
Purchase #6	$229.64	9.567%	$251.6097	$251.61	$251.60	$251.60
Purchase #7	$203.41	3.209%	$209.9374	$209.94	$209.95	$209.90
7 purchase totals =	$970.62		$1,049.7315	$1,049.73	$1,049.65	$1,049.80