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	$243.66	11.634%	$272.0074	$272.01	$272.00	$272.00
Purchase #2	$49.43	7.558%	$53.1659	$53.17	$53.15	$53.20
Purchase #3	$166.79	7.424%	$179.1725	$179.17	$179.15	$179.20
Purchase #4	$137.28	13.858%	$156.3043	$156.30	$156.30	$156.30
Purchase #5	$78.47	4.456%	$81.9666	$81.97	$81.95	$82.00
Purchase #6	$237.41	5.401%	$250.2325	$250.23	$250.25	$250.20
Purchase #7	$137.65	10.512%	$152.1198	$152.12	$152.10	$152.10
7 purchase totals =	$1,050.69		$1,144.9690	$1,144.97	$1,144.90	$1,145.00