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	$111.53	12.740%	$125.7389	$125.74	$125.75	$125.70
Purchase #2	$57.82	6.384%	$61.5112	$61.51	$61.50	$61.50
Purchase #3	$37.69	6.771%	$40.242	$40.24	$40.25	$40.20
Purchase #4	$99.54	5.102%	$104.6185	$104.62	$104.60	$104.60
Purchase #5	$167.64	9.748%	$183.9815	$183.98	$184.00	$184.00
Purchase #6	$37.49	11.824%	$41.9228	$41.92	$41.90	$41.90
Purchase #7	$154.64	5.129%	$162.5715	$162.57	$162.55	$162.60
7 purchase totals =	$666.35		$720.5864	$720.58	$720.55	$720.50