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	$145.88	7.721%	$157.1434	$157.14	$157.15	$157.10
Purchase #2	$78.81	8.315%	$85.3631	$85.36	$85.35	$85.40
Purchase #3	$73.76	5.720%	$77.9791	$77.98	$78.00	$78.00
Purchase #4	$233.47	13.168%	$264.2133	$264.21	$264.20	$264.20
Purchase #5	$103.52	5.781%	$109.5045	$109.50	$109.50	$109.50
Purchase #6	$99.53	5.743%	$105.246	$105.25	$105.25	$105.20
Purchase #7	$29.85	10.148%	$32.8792	$32.88	$32.90	$32.90
7 purchase totals =	$764.82		$832.3286	$832.32	$832.35	$832.30