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	$112.53	10.353%	$124.1802	$124.18	$124.20	$124.20
Purchase #2	$95.37	4.292%	$99.4633	$99.46	$99.45	$99.50
Purchase #3	$150.53	4.241%	$156.914	$156.91	$156.90	$156.90
Purchase #4	$220.70	12.111%	$247.429	$247.43	$247.45	$247.40
Purchase #5	$86.31	11.806%	$96.4998	$96.50	$96.50	$96.50
Purchase #6	$161.68	10.818%	$179.1705	$179.17	$179.15	$179.20
Purchase #7	$159.40	6.704%	$170.0862	$170.09	$170.10	$170.10
7 purchase totals =	$986.52		$1,073.7430	$1,073.74	$1,073.75	$1,073.80