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	$147.37	13.789%	$167.6908	$167.69	$167.70	$167.70
Purchase #2	$5.60	11.270%	$6.2311	$6.23	$6.25	$6.20
Purchase #3	$112.36	5.356%	$118.378	$118.38	$118.40	$118.40
Purchase #4	$88.55	12.400%	$99.5302	$99.53	$99.55	$99.50
Purchase #5	$27.72	11.360%	$30.869	$30.87	$30.85	$30.90
Purchase #6	$202.52	11.258%	$225.3197	$225.32	$225.30	$225.30
Purchase #7	$65.47	9.563%	$71.7309	$71.73	$71.75	$71.70
7 purchase totals =	$649.59		$719.7497	$719.75	$719.80	$719.70