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	$142.47	7.631%	$153.3419	$153.34	$153.35	$153.30
Purchase #2	$103.47	12.801%	$116.7152	$116.72	$116.70	$116.70
Purchase #3	$127.59	9.536%	$139.757	$139.76	$139.75	$139.80
Purchase #4	$220.28	6.828%	$235.3207	$235.32	$235.30	$235.30
Purchase #5	$82.59	8.573%	$89.6704	$89.67	$89.65	$89.70
Purchase #6	$171.73	4.477%	$179.4184	$179.42	$179.40	$179.40
Purchase #7	$92.32	11.869%	$103.2775	$103.28	$103.30	$103.30
7 purchase totals =	$940.45		$1,017.5011	$1,017.51	$1,017.45	$1,017.50