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	$210.50	13.444%	$238.7996	$238.80	$238.80	$238.80
Purchase #2	$12.46	3.199%	$12.8586	$12.86	$12.85	$12.90
Purchase #3	$174.72	7.184%	$187.2719	$187.27	$187.25	$187.30
Purchase #4	$88.42	4.183%	$92.1186	$92.12	$92.10	$92.10
Purchase #5	$40.77	5.292%	$42.9275	$42.93	$42.95	$42.90
Purchase #6	$30.46	10.447%	$33.6422	$33.64	$33.65	$33.60
Purchase #7	$93.45	5.605%	$98.6879	$98.69	$98.70	$98.70
7 purchase totals =	$650.78		$706.3063	$706.31	$706.30	$706.30