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	$76.58	7.463%	$82.2952	$82.30	$82.30	$82.30
Purchase #2	$54.72	9.216%	$59.763	$59.76	$59.75	$59.80
Purchase #3	$69.33	9.596%	$75.9829	$75.98	$76.00	$76.00
Purchase #4	$28.82	7.580%	$31.0046	$31.00	$31.00	$31.00
Purchase #5	$153.33	4.850%	$160.7665	$160.77	$160.75	$160.80
Purchase #6	$166.50	3.243%	$171.8996	$171.90	$171.90	$171.90
Purchase #7	$102.34	13.579%	$116.2367	$116.24	$116.25	$116.20
7 purchase totals =	$651.62		$697.9485	$697.95	$697.95	$698.00