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	$82.49	9.277%	$90.1426	$90.14	$90.15	$90.10
Purchase #2	$91.71	11.169%	$101.9531	$101.95	$101.95	$102.00
Purchase #3	$34.88	6.280%	$37.0705	$37.07	$37.05	$37.10
Purchase #4	$185.49	6.539%	$197.6192	$197.62	$197.60	$197.60
Purchase #5	$19.78	9.380%	$21.6354	$21.64	$21.65	$21.60
Purchase #6	$34.51	9.113%	$37.6549	$37.65	$37.65	$37.70
Purchase #7	$149.61	11.535%	$166.8675	$166.87	$166.85	$166.90
7 purchase totals =	$598.47		$652.9432	$652.94	$652.90	$653.00