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	$203.42	12.669%	$229.1913	$229.19	$229.20	$229.20
Purchase #2	$201.56	11.187%	$224.1085	$224.11	$224.10	$224.10
Purchase #3	$96.25	3.767%	$99.8757	$99.88	$99.90	$99.90
Purchase #4	$85.50	4.669%	$89.492	$89.49	$89.50	$89.50
Purchase #5	$127.50	7.675%	$137.2856	$137.29	$137.30	$137.30
Purchase #6	$162.37	5.487%	$171.2792	$171.28	$171.30	$171.30
Purchase #7	$146.98	6.504%	$156.5396	$156.54	$156.55	$156.50
7 purchase totals =	$1,023.58		$1,107.7719	$1,107.78	$1,107.85	$1,107.80