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	$96.34	9.113%	$105.1195	$105.12	$105.10	$105.10
Purchase #2	$77.27	13.805%	$87.9371	$87.94	$87.95	$87.90
Purchase #3	$92.66	6.797%	$98.9581	$98.96	$98.95	$99.00
Purchase #4	$200.93	10.132%	$221.2882	$221.29	$221.30	$221.30
Purchase #5	$217.66	5.621%	$229.8947	$229.89	$229.90	$229.90
Purchase #6	$165.33	11.607%	$184.5199	$184.52	$184.50	$184.50
Purchase #7	$155.37	8.549%	$168.6526	$168.65	$168.65	$168.70
7 purchase totals =	$1,005.56		$1,096.3701	$1,096.37	$1,096.35	$1,096.40