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	$92.47	3.310%	$95.5308	$95.53	$95.55	$95.50
Purchase #2	$31.70	6.447%	$33.7437	$33.74	$33.75	$33.70
Purchase #3	$151.42	4.230%	$157.8251	$157.83	$157.85	$157.80
Purchase #4	$73.72	9.112%	$80.4374	$80.44	$80.45	$80.40
Purchase #5	$83.71	8.526%	$90.8471	$90.85	$90.85	$90.80
Purchase #6	$99.26	9.350%	$108.5408	$108.54	$108.55	$108.50
Purchase #7	$80.27	11.181%	$89.245	$89.25	$89.25	$89.20
7 purchase totals =	$612.55		$656.1699	$656.18	$656.25	$655.90