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	$94.89	11.253%	$105.568	$105.57	$105.55	$105.60
Purchase #2	$173.46	4.789%	$181.767	$181.77	$181.75	$181.80
Purchase #3	$57.57	3.447%	$59.5544	$59.55	$59.55	$59.60
Purchase #4	$184.86	9.393%	$202.2239	$202.22	$202.20	$202.20
Purchase #5	$142.46	13.530%	$161.7348	$161.73	$161.75	$161.70
Purchase #6	$166.59	12.274%	$187.0373	$187.04	$187.05	$187.00
Purchase #7	$55.42	10.629%	$61.3106	$61.31	$61.30	$61.30
7 purchase totals =	$875.25		$959.1960	$959.19	$959.15	$959.20