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	$247.88	3.180%	$255.7626	$255.76	$255.75	$255.80
Purchase #2	$175.48	9.298%	$191.7961	$191.80	$191.80	$191.80
Purchase #3	$100.73	4.354%	$105.1158	$105.12	$105.10	$105.10
Purchase #4	$148.39	5.351%	$156.3303	$156.33	$156.35	$156.30
Purchase #5	$25.83	8.108%	$27.9243	$27.92	$27.90	$27.90
Purchase #6	$94.30	11.265%	$104.9229	$104.92	$104.90	$104.90
Purchase #7	$219.94	3.179%	$226.9319	$226.93	$226.95	$226.90
7 purchase totals =	$1,012.55		$1,068.7839	$1,068.78	$1,068.75	$1,068.70