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	$83.48	10.797%	$92.4933	$92.49	$92.50	$92.50
Purchase #2	$56.28	7.751%	$60.6423	$60.64	$60.65	$60.60
Purchase #3	$135.82	5.857%	$143.775	$143.78	$143.80	$143.80
Purchase #4	$115.94	6.251%	$123.1874	$123.19	$123.20	$123.20
Purchase #5	$131.34	11.845%	$146.8972	$146.90	$146.90	$146.90
Purchase #6	$96.30	13.692%	$109.4854	$109.49	$109.50	$109.50
Purchase #7	$77.98	6.109%	$82.7438	$82.74	$82.75	$82.70
7 purchase totals =	$697.14		$759.2244	$759.23	$759.30	$759.20