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	$98.25	11.215%	$109.2687	$109.27	$109.25	$109.30
Purchase #2	$164.29	3.271%	$169.6639	$169.66	$169.65	$169.70
Purchase #3	$130.92	10.314%	$144.4231	$144.42	$144.40	$144.40
Purchase #4	$90.67	6.520%	$96.5817	$96.58	$96.60	$96.60
Purchase #5	$83.68	10.327%	$92.3216	$92.32	$92.30	$92.30
Purchase #6	$153.95	10.722%	$170.4565	$170.46	$170.45	$170.50
Purchase #7	$23.52	6.530%	$25.0559	$25.06	$25.05	$25.10
7 purchase totals =	$745.28		$807.7714	$807.77	$807.70	$807.90