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	$93.78	12.731%	$105.7191	$105.72	$105.70	$105.70
Purchase #2	$241.32	4.226%	$251.5182	$251.52	$251.50	$251.50
Purchase #3	$41.48	3.790%	$43.0521	$43.05	$43.05	$43.10
Purchase #4	$248.77	11.820%	$278.1746	$278.17	$278.15	$278.20
Purchase #5	$101.96	6.846%	$108.9402	$108.94	$108.95	$108.90
Purchase #6	$242.56	3.798%	$251.7724	$251.77	$251.75	$251.80
Purchase #7	$64.31	13.273%	$72.8459	$72.85	$72.85	$72.80
7 purchase totals =	$1,034.18		$1,112.0225	$1,112.02	$1,111.95	$1,112.00