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	$244.37	13.384%	$277.0765	$277.08	$277.10	$277.10
Purchase #2	$207.28	5.221%	$218.1021	$218.10	$218.10	$218.10
Purchase #3	$65.27	10.381%	$72.0457	$72.05	$72.05	$72.00
Purchase #4	$120.58	5.335%	$127.0129	$127.01	$127.00	$127.00
Purchase #5	$49.51	6.233%	$52.596	$52.60	$52.60	$52.60
Purchase #6	$91.38	12.830%	$103.1041	$103.10	$103.10	$103.10
Purchase #7	$109.31	11.568%	$121.955	$121.96	$121.95	$122.00
7 purchase totals =	$887.70		$971.8923	$971.90	$971.90	$971.90