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	$177.63	6.551%	$189.2665	$189.27	$189.25	$189.30
Purchase #2	$209.83	11.837%	$234.6676	$234.67	$234.65	$234.70
Purchase #3	$196.94	6.309%	$209.3649	$209.36	$209.35	$209.40
Purchase #4	$76.52	11.113%	$85.0237	$85.02	$85.00	$85.00
Purchase #5	$89.91	12.274%	$100.9456	$100.95	$100.95	$100.90
Purchase #6	$64.68	8.104%	$69.9217	$69.92	$69.90	$69.90
Purchase #7	$149.96	11.846%	$167.7243	$167.72	$167.70	$167.70
7 purchase totals =	$965.47		$1,056.9143	$1,056.91	$1,056.80	$1,056.90