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	$177.87	6.508%	$189.4458	$189.45	$189.45	$189.40
Purchase #2	$249.98	9.417%	$273.5206	$273.52	$273.50	$273.50
Purchase #3	$38.99	7.841%	$42.0472	$42.05	$42.05	$42.00
Purchase #4	$26.45	7.419%	$28.4123	$28.41	$28.40	$28.40
Purchase #5	$230.85	11.136%	$256.5575	$256.56	$256.55	$256.60
Purchase #6	$92.31	6.453%	$98.2668	$98.27	$98.25	$98.30
Purchase #7	$167.34	3.313%	$172.884	$172.88	$172.90	$172.90
7 purchase totals =	$983.79		$1,061.1342	$1,061.14	$1,061.10	$1,061.10