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	$95.97	13.522%	$108.9471	$108.95	$108.95	$108.90
Purchase #2	$190.79	3.137%	$196.7751	$196.78	$196.80	$196.80
Purchase #3	$237.55	11.116%	$263.9561	$263.96	$263.95	$264.00
Purchase #4	$78.32	11.501%	$87.3276	$87.33	$87.35	$87.30
Purchase #5	$159.72	11.592%	$178.2347	$178.23	$178.25	$178.20
Purchase #6	$159.27	7.841%	$171.7584	$171.76	$171.75	$171.80
Purchase #7	$167.43	13.409%	$189.8807	$189.88	$189.90	$189.90
7 purchase totals =	$1,089.05		$1,196.8797	$1,196.89	$1,196.95	$1,196.90