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	$173.86	9.199%	$189.8534	$189.85	$189.85	$189.90
Purchase #2	$245.38	11.245%	$272.973	$272.97	$272.95	$273.00
Purchase #3	$136.60	7.171%	$146.3956	$146.40	$146.40	$146.40
Purchase #4	$181.90	7.823%	$196.13	$196.13	$196.15	$196.10
Purchase #5	$75.70	4.274%	$78.9354	$78.94	$78.95	$78.90
Purchase #6	$92.36	11.168%	$102.6748	$102.67	$102.65	$102.70
Purchase #7	$89.52	13.345%	$101.4664	$101.47	$101.45	$101.50
7 purchase totals =	$995.32		$1,088.4286	$1,088.43	$1,088.40	$1,088.50