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	$130.97	11.121%	$145.5352	$145.54	$145.55	$145.50
Purchase #2	$148.71	13.278%	$168.4557	$168.46	$168.45	$168.50
Purchase #3	$249.57	7.552%	$268.4175	$268.42	$268.40	$268.40
Purchase #4	$33.49	12.174%	$37.5671	$37.57	$37.55	$37.60
Purchase #5	$173.27	4.509%	$181.0827	$181.08	$181.10	$181.10
Purchase #6	$33.59	4.791%	$35.1993	$35.20	$35.20	$35.20
Purchase #7	$206.40	3.374%	$213.3639	$213.36	$213.35	$213.40
7 purchase totals =	$976.00		$1,049.6214	$1,049.63	$1,049.60	$1,049.70