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	$148.89	11.671%	$166.267	$166.27	$166.25	$166.30
Purchase #2	$6.31	8.623%	$6.8541	$6.85	$6.85	$6.90
Purchase #3	$140.61	8.745%	$152.9063	$152.91	$152.90	$152.90
Purchase #4	$85.81	12.329%	$96.3895	$96.39	$96.40	$96.40
Purchase #5	$195.80	10.200%	$215.7716	$215.77	$215.75	$215.80
Purchase #6	$36.93	8.217%	$39.9645	$39.96	$39.95	$40.00
Purchase #7	$150.89	4.790%	$158.1176	$158.12	$158.10	$158.10
7 purchase totals =	$765.24		$836.2706	$836.27	$836.20	$836.40