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	$204.27	3.356%	$211.1253	$211.13	$211.15	$211.10
Purchase #2	$202.64	10.321%	$223.5545	$223.55	$223.55	$223.60
Purchase #3	$24.52	4.573%	$25.6413	$25.64	$25.65	$25.60
Purchase #4	$139.31	11.458%	$155.2721	$155.27	$155.25	$155.30
Purchase #5	$78.82	3.123%	$81.2815	$81.28	$81.30	$81.30
Purchase #6	$81.77	11.109%	$90.8538	$90.85	$90.85	$90.90
Purchase #7	$84.63	13.148%	$95.7572	$95.76	$95.75	$95.80
7 purchase totals =	$815.96		$883.4857	$883.48	$883.50	$883.60