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	$95.57	8.653%	$103.8397	$103.84	$103.85	$103.80
Purchase #2	$50.43	12.874%	$56.9224	$56.92	$56.90	$56.90
Purchase #3	$162.62	3.395%	$168.1409	$168.14	$168.15	$168.10
Purchase #4	$64.57	7.339%	$69.3088	$69.31	$69.30	$69.30
Purchase #5	$40.80	11.651%	$45.5536	$45.55	$45.55	$45.60
Purchase #6	$185.35	10.749%	$205.2733	$205.27	$205.25	$205.30
Purchase #7	$172.71	7.846%	$186.2608	$186.26	$186.25	$186.30
7 purchase totals =	$772.05		$835.2995	$835.29	$835.25	$835.30