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	$189.66	3.655%	$196.5921	$196.59	$196.60	$196.60
Purchase #2	$250.77	12.163%	$281.2712	$281.27	$281.25	$281.30
Purchase #3	$192.67	13.359%	$218.4088	$218.41	$218.40	$218.40
Purchase #4	$95.85	12.642%	$107.9674	$107.97	$107.95	$108.00
Purchase #5	$249.64	3.701%	$258.8792	$258.88	$258.90	$258.90
Purchase #6	$208.56	7.365%	$223.9204	$223.92	$223.90	$223.90
Purchase #7	$19.55	3.548%	$20.2436	$20.24	$20.25	$20.20
7 purchase totals =	$1,206.70		$1,307.2827	$1,307.28	$1,307.25	$1,307.30