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	$70.76	13.493%	$80.3076	$80.31	$80.30	$80.30
Purchase #2	$6.95	12.834%	$7.842	$7.84	$7.85	$7.80
Purchase #3	$36.31	10.387%	$40.0815	$40.08	$40.10	$40.10
Purchase #4	$80.72	13.750%	$91.819	$91.82	$91.80	$91.80
Purchase #5	$88.99	11.795%	$99.4864	$99.49	$99.50	$99.50
Purchase #6	$65.32	5.847%	$69.1393	$69.14	$69.15	$69.10
Purchase #7	$57.70	3.220%	$59.5579	$59.56	$59.55	$59.60
7 purchase totals =	$406.75		$448.2337	$448.24	$448.25	$448.20