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	$12.76	8.809%	$13.884	$13.88	$13.90	$13.90
Purchase #2	$72.26	5.571%	$76.2856	$76.29	$76.30	$76.30
Purchase #3	$9.88	13.700%	$11.2336	$11.23	$11.25	$11.20
Purchase #4	$53.69	8.179%	$58.0813	$58.08	$58.10	$58.10
Purchase #5	$208.69	6.393%	$222.0316	$222.03	$222.05	$222.00
Purchase #6	$198.99	8.622%	$216.1469	$216.15	$216.15	$216.10
Purchase #7	$78.56	13.412%	$89.0965	$89.10	$89.10	$89.10
7 purchase totals =	$634.83		$686.7595	$686.76	$686.85	$686.70