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	$204.31	8.859%	$222.4098	$222.41	$222.40	$222.40
Purchase #2	$136.35	7.173%	$146.1304	$146.13	$146.15	$146.10
Purchase #3	$83.63	5.833%	$88.5081	$88.51	$88.50	$88.50
Purchase #4	$27.75	7.538%	$29.8418	$29.84	$29.85	$29.80
Purchase #5	$56.57	11.839%	$63.2673	$63.27	$63.25	$63.30
Purchase #6	$48.59	12.728%	$54.7745	$54.77	$54.75	$54.80
Purchase #7	$209.93	6.392%	$223.3487	$223.35	$223.35	$223.30
7 purchase totals =	$767.13		$828.2806	$828.28	$828.25	$828.20