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	$96.63	13.147%	$109.3339	$109.33	$109.35	$109.30
Purchase #2	$174.38	6.315%	$185.3921	$185.39	$185.40	$185.40
Purchase #3	$71.50	13.848%	$81.4013	$81.40	$81.40	$81.40
Purchase #4	$216.41	11.313%	$240.8925	$240.89	$240.90	$240.90
Purchase #5	$223.49	7.267%	$239.731	$239.73	$239.75	$239.70
Purchase #6	$177.93	3.848%	$184.7767	$184.78	$184.80	$184.80
Purchase #7	$8.93	12.764%	$10.0698	$10.07	$10.05	$10.10
7 purchase totals =	$969.27		$1,051.5973	$1,051.59	$1,051.65	$1,051.60