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	$63.78	12.487%	$71.7442	$71.74	$71.75	$71.70
Purchase #2	$33.29	11.602%	$37.1523	$37.15	$37.15	$37.20
Purchase #3	$222.85	3.707%	$231.111	$231.11	$231.10	$231.10
Purchase #4	$213.71	11.826%	$238.9833	$238.98	$239.00	$239.00
Purchase #5	$157.41	10.608%	$174.1081	$174.11	$174.10	$174.10
Purchase #6	$48.61	9.673%	$53.312	$53.31	$53.30	$53.30
Purchase #7	$70.74	10.585%	$78.2278	$78.23	$78.25	$78.20
7 purchase totals =	$810.39		$884.6387	$884.63	$884.65	$884.60