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	$180.76	8.589%	$196.2855	$196.29	$196.30	$196.30
Purchase #2	$57.98	13.610%	$65.8711	$65.87	$65.85	$65.90
Purchase #3	$185.86	7.373%	$199.5635	$199.56	$199.55	$199.60
Purchase #4	$181.60	10.274%	$200.2576	$200.26	$200.25	$200.30
Purchase #5	$93.28	5.145%	$98.0793	$98.08	$98.10	$98.10
Purchase #6	$40.95	8.258%	$44.3317	$44.33	$44.35	$44.30
Purchase #7	$147.82	4.687%	$154.7483	$154.75	$154.75	$154.70
7 purchase totals =	$888.25		$959.1370	$959.14	$959.15	$959.20