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	$205.98	7.675%	$221.789	$221.79	$221.80	$221.80
Purchase #2	$16.72	10.183%	$18.4226	$18.42	$18.40	$18.40
Purchase #3	$249.99	5.689%	$264.2119	$264.21	$264.20	$264.20
Purchase #4	$25.68	11.336%	$28.5911	$28.59	$28.60	$28.60
Purchase #5	$100.44	3.621%	$104.0769	$104.08	$104.10	$104.10
Purchase #6	$177.82	10.539%	$196.5604	$196.56	$196.55	$196.60
Purchase #7	$80.61	12.585%	$90.7548	$90.75	$90.75	$90.80
7 purchase totals =	$857.24		$924.4067	$924.40	$924.40	$924.50