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	$150.31	3.613%	$155.7407	$155.74	$155.75	$155.70
Purchase #2	$248.75	13.213%	$281.6173	$281.62	$281.60	$281.60
Purchase #3	$16.41	12.624%	$18.4816	$18.48	$18.50	$18.50
Purchase #4	$146.60	6.709%	$156.4354	$156.44	$156.45	$156.40
Purchase #5	$80.74	6.399%	$85.9066	$85.91	$85.90	$85.90
Purchase #6	$213.28	9.345%	$233.211	$233.21	$233.20	$233.20
Purchase #7	$159.63	5.832%	$168.9396	$168.94	$168.95	$168.90
7 purchase totals =	$1,015.72		$1,100.3322	$1,100.34	$1,100.35	$1,100.20