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	$146.83	5.146%	$154.3859	$154.39	$154.40	$154.40
Purchase #2	$31.66	6.859%	$33.8316	$33.83	$33.85	$33.80
Purchase #3	$89.89	10.605%	$99.4228	$99.42	$99.40	$99.40
Purchase #4	$67.82	10.765%	$75.1208	$75.12	$75.10	$75.10
Purchase #5	$84.38	11.737%	$94.2837	$94.28	$94.30	$94.30
Purchase #6	$35.26	4.685%	$36.9119	$36.91	$36.90	$36.90
Purchase #7	$118.61	12.849%	$133.8502	$133.85	$133.85	$133.90
7 purchase totals =	$574.45		$627.8069	$627.80	$627.80	$627.80