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	$149.95	11.304%	$166.9003	$166.90	$166.90	$166.90
Purchase #2	$84.95	6.795%	$90.7224	$90.72	$90.70	$90.70
Purchase #3	$54.32	7.820%	$58.5678	$58.57	$58.55	$58.60
Purchase #4	$168.57	11.191%	$187.4347	$187.43	$187.45	$187.40
Purchase #5	$193.34	6.161%	$205.2517	$205.25	$205.25	$205.30
Purchase #6	$78.51	8.615%	$85.2736	$85.27	$85.25	$85.30
Purchase #7	$215.42	3.206%	$222.3264	$222.33	$222.35	$222.30
7 purchase totals =	$945.06		$1,016.4769	$1,016.47	$1,016.45	$1,016.50