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	$98.73	5.609%	$104.2678	$104.27	$104.25	$104.30
Purchase #2	$77.73	6.356%	$82.6705	$82.67	$82.65	$82.70
Purchase #3	$212.69	12.430%	$239.1274	$239.13	$239.15	$239.10
Purchase #4	$56.82	4.586%	$59.4258	$59.43	$59.45	$59.40
Purchase #5	$243.27	11.391%	$270.9809	$270.98	$271.00	$271.00
Purchase #6	$228.50	9.294%	$249.7368	$249.74	$249.75	$249.70
Purchase #7	$125.90	3.471%	$130.27	$130.27	$130.25	$130.30
7 purchase totals =	$1,043.64		$1,136.4792	$1,136.49	$1,136.50	$1,136.50