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	$184.36	7.574%	$198.3234	$198.32	$198.30	$198.30
Purchase #2	$146.70	13.478%	$166.4722	$166.47	$166.45	$166.50
Purchase #3	$245.42	12.249%	$275.4815	$275.48	$275.50	$275.50
Purchase #4	$82.45	7.526%	$88.6552	$88.66	$88.65	$88.70
Purchase #5	$109.43	5.143%	$115.058	$115.06	$115.05	$115.10
Purchase #6	$157.56	5.861%	$166.7946	$166.79	$166.80	$166.80
Purchase #7	$66.54	5.794%	$70.3953	$70.40	$70.40	$70.40
7 purchase totals =	$992.46		$1,081.1802	$1,081.18	$1,081.15	$1,081.30