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	$63.98	11.551%	$71.3703	$71.37	$71.35	$71.40
Purchase #2	$209.99	4.233%	$218.8789	$218.88	$218.90	$218.90
Purchase #3	$9.55	13.144%	$10.8053	$10.81	$10.80	$10.80
Purchase #4	$121.41	6.841%	$129.7157	$129.72	$129.70	$129.70
Purchase #5	$73.64	11.754%	$82.2956	$82.30	$82.30	$82.30
Purchase #6	$101.82	9.251%	$111.2394	$111.24	$111.25	$111.20
Purchase #7	$91.71	11.499%	$102.2557	$102.26	$102.25	$102.30
7 purchase totals =	$672.10		$726.5609	$726.58	$726.55	$726.60