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	$58.33	9.835%	$64.0668	$64.07	$64.05	$64.10
Purchase #2	$33.36	13.477%	$37.8559	$37.86	$37.85	$37.90
Purchase #3	$117.85	8.222%	$127.5396	$127.54	$127.55	$127.50
Purchase #4	$207.33	5.499%	$218.7311	$218.73	$218.75	$218.70
Purchase #5	$150.77	9.852%	$165.6239	$165.62	$165.60	$165.60
Purchase #6	$107.39	11.646%	$119.8966	$119.90	$119.90	$119.90
Purchase #7	$211.49	11.298%	$235.3841	$235.38	$235.40	$235.40
7 purchase totals =	$886.52		$969.0980	$969.10	$969.10	$969.10