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	$148.29	8.347%	$160.6678	$160.67	$160.65	$160.70
Purchase #2	$102.89	9.776%	$112.9485	$112.95	$112.95	$112.90
Purchase #3	$111.43	10.708%	$123.3619	$123.36	$123.35	$123.40
Purchase #4	$80.93	10.108%	$89.1104	$89.11	$89.10	$89.10
Purchase #5	$46.71	5.295%	$49.1833	$49.18	$49.20	$49.20
Purchase #6	$40.41	9.444%	$44.2263	$44.23	$44.25	$44.20
Purchase #7	$123.44	3.809%	$128.1418	$128.14	$128.15	$128.10
7 purchase totals =	$654.10		$707.6400	$707.64	$707.65	$707.60