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	$113.42	12.833%	$127.9752	$127.98	$128.00	$128.00
Purchase #2	$131.43	9.164%	$143.4742	$143.47	$143.45	$143.50
Purchase #3	$6.96	12.478%	$7.8285	$7.83	$7.85	$7.80
Purchase #4	$221.29	10.411%	$244.3285	$244.33	$244.35	$244.30
Purchase #5	$224.80	11.585%	$250.8431	$250.84	$250.85	$250.80
Purchase #6	$168.57	13.654%	$191.5865	$191.59	$191.60	$191.60
Purchase #7	$189.35	9.790%	$207.8874	$207.89	$207.90	$207.90
7 purchase totals =	$1,055.82		$1,173.9234	$1,173.93	$1,174.00	$1,173.90