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	$92.48	9.666%	$101.4191	$101.42	$101.40	$101.40
Purchase #2	$80.41	3.558%	$83.271	$83.27	$83.25	$83.30
Purchase #3	$164.37	13.455%	$186.486	$186.49	$186.50	$186.50
Purchase #4	$195.45	5.814%	$206.8135	$206.81	$206.80	$206.80
Purchase #5	$85.87	3.743%	$89.0841	$89.08	$89.10	$89.10
Purchase #6	$39.89	6.331%	$42.4154	$42.42	$42.40	$42.40
Purchase #7	$129.73	12.668%	$146.1642	$146.16	$146.15	$146.20
7 purchase totals =	$788.20		$855.6533	$855.65	$855.60	$855.70