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	$202.84	11.793%	$226.7609	$226.76	$226.75	$226.80
Purchase #2	$36.73	8.708%	$39.9284	$39.93	$39.95	$39.90
Purchase #3	$99.27	10.563%	$109.7559	$109.76	$109.75	$109.80
Purchase #4	$81.97	11.670%	$91.5359	$91.54	$91.55	$91.50
Purchase #5	$54.73	10.579%	$60.5199	$60.52	$60.50	$60.50
Purchase #6	$152.83	7.576%	$164.4084	$164.41	$164.40	$164.40
Purchase #7	$19.76	3.523%	$20.4561	$20.46	$20.45	$20.50
7 purchase totals =	$648.13		$713.3655	$713.38	$713.35	$713.40