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	$145.83	13.190%	$165.065	$165.07	$165.05	$165.10
Purchase #2	$198.59	3.838%	$206.2119	$206.21	$206.20	$206.20
Purchase #3	$108.75	8.417%	$117.9035	$117.90	$117.90	$117.90
Purchase #4	$78.78	13.824%	$89.6705	$89.67	$89.65	$89.70
Purchase #5	$130.92	11.121%	$145.4796	$145.48	$145.50	$145.50
Purchase #6	$177.53	9.712%	$194.7717	$194.77	$194.75	$194.80
Purchase #7	$86.66	6.224%	$92.0537	$92.05	$92.05	$92.10
7 purchase totals =	$927.06		$1,011.1559	$1,011.15	$1,011.10	$1,011.30