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	$123.82	5.393%	$130.4976	$130.50	$130.50	$130.50
Purchase #2	$42.53	5.232%	$44.7552	$44.76	$44.75	$44.80
Purchase #3	$135.97	3.362%	$140.5413	$140.54	$140.55	$140.50
Purchase #4	$111.64	6.665%	$119.0808	$119.08	$119.10	$119.10
Purchase #5	$232.36	3.597%	$240.718	$240.72	$240.70	$240.70
Purchase #6	$222.59	13.862%	$253.4454	$253.45	$253.45	$253.40
Purchase #7	$138.68	5.649%	$146.514	$146.51	$146.50	$146.50
7 purchase totals =	$1,007.59		$1,075.5523	$1,075.56	$1,075.55	$1,075.50