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	$196.33	5.629%	$207.3814	$207.38	$207.40	$207.40
Purchase #2	$114.98	13.666%	$130.6932	$130.69	$130.70	$130.70
Purchase #3	$71.91	9.845%	$78.9895	$78.99	$79.00	$79.00
Purchase #4	$132.35	5.362%	$139.4466	$139.45	$139.45	$139.40
Purchase #5	$85.31	6.383%	$90.7553	$90.76	$90.75	$90.80
Purchase #6	$153.85	10.204%	$169.5489	$169.55	$169.55	$169.50
Purchase #7	$100.32	4.562%	$104.8966	$104.90	$104.90	$104.90
7 purchase totals =	$855.05		$921.7115	$921.72	$921.75	$921.70