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	$92.35	3.382%	$95.4733	$95.47	$95.45	$95.50
Purchase #2	$28.33	10.744%	$31.3738	$31.37	$31.35	$31.40
Purchase #3	$165.34	11.299%	$184.0218	$184.02	$184.00	$184.00
Purchase #4	$50.65	9.393%	$55.4076	$55.41	$55.40	$55.40
Purchase #5	$119.96	3.292%	$123.9091	$123.91	$123.90	$123.90
Purchase #6	$12.33	9.774%	$13.5351	$13.54	$13.55	$13.50
Purchase #7	$55.30	11.327%	$61.5638	$61.56	$61.55	$61.60
7 purchase totals =	$524.26		$565.2845	$565.28	$565.20	$565.30