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	$84.80	12.107%	$95.0667	$95.07	$95.05	$95.10
Purchase #2	$55.97	10.162%	$61.6577	$61.66	$61.65	$61.70
Purchase #3	$243.86	4.537%	$254.9239	$254.92	$254.90	$254.90
Purchase #4	$81.68	9.705%	$89.607	$89.61	$89.60	$89.60
Purchase #5	$48.31	9.858%	$53.0724	$53.07	$53.05	$53.10
Purchase #6	$96.59	13.306%	$109.4423	$109.44	$109.45	$109.40
Purchase #7	$101.42	6.526%	$108.0387	$108.04	$108.05	$108.00
7 purchase totals =	$712.63		$771.8087	$771.81	$771.75	$771.80