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	$44.69	11.832%	$49.9777	$49.98	$50.00	$50.00
Purchase #2	$43.56	13.638%	$49.5007	$49.50	$49.50	$49.50
Purchase #3	$94.64	11.635%	$105.6514	$105.65	$105.65	$105.70
Purchase #4	$5.54	10.296%	$6.1104	$6.11	$6.10	$6.10
Purchase #5	$142.28	6.585%	$151.6491	$151.65	$151.65	$151.60
Purchase #6	$69.86	12.769%	$78.7804	$78.78	$78.80	$78.80
Purchase #7	$45.27	4.356%	$47.242	$47.24	$47.25	$47.20
7 purchase totals =	$445.84		$488.9117	$488.91	$488.95	$488.90