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	$230.51	6.604%	$245.7329	$245.73	$245.75	$245.70
Purchase #2	$189.32	3.652%	$196.234	$196.23	$196.25	$196.20
Purchase #3	$63.39	3.695%	$65.7323	$65.73	$65.75	$65.70
Purchase #4	$85.39	12.551%	$96.1073	$96.11	$96.10	$96.10
Purchase #5	$52.62	3.277%	$54.3444	$54.34	$54.35	$54.30
Purchase #6	$160.95	3.441%	$166.4883	$166.49	$166.50	$166.50
Purchase #7	$232.76	8.835%	$253.3243	$253.32	$253.30	$253.30
7 purchase totals =	$1,014.94		$1,077.9635	$1,077.95	$1,078.00	$1,077.80