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	$39.50	4.825%	$41.4059	$41.41	$41.40	$41.40
Purchase #2	$188.44	4.321%	$196.5825	$196.58	$196.60	$196.60
Purchase #3	$100.68	11.277%	$112.0337	$112.03	$112.05	$112.00
Purchase #4	$151.36	3.476%	$156.6213	$156.62	$156.60	$156.60
Purchase #5	$118.42	4.596%	$123.8626	$123.86	$123.85	$123.90
Purchase #6	$136.75	9.799%	$150.1501	$150.15	$150.15	$150.20
Purchase #7	$124.81	3.618%	$129.3256	$129.33	$129.35	$129.30
7 purchase totals =	$859.96		$909.9817	$909.98	$910.00	$910.00