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	$172.29	5.135%	$181.1371	$181.14	$181.15	$181.10
Purchase #2	$113.40	13.325%	$128.5106	$128.51	$128.50	$128.50
Purchase #3	$116.98	3.271%	$120.8064	$120.81	$120.80	$120.80
Purchase #4	$211.66	5.712%	$223.75	$223.75	$223.75	$223.80
Purchase #5	$180.72	8.315%	$195.7469	$195.75	$195.75	$195.70
Purchase #6	$36.63	3.113%	$37.7703	$37.77	$37.75	$37.80
Purchase #7	$187.51	12.463%	$210.8794	$210.88	$210.90	$210.90
7 purchase totals =	$1,019.19		$1,098.6007	$1,098.61	$1,098.60	$1,098.60