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	$102.67	3.209%	$105.9647	$105.96	$105.95	$106.00
Purchase #2	$107.41	9.665%	$117.7912	$117.79	$117.80	$117.80
Purchase #3	$149.91	11.830%	$167.6444	$167.64	$167.65	$167.60
Purchase #4	$168.31	6.179%	$178.7099	$178.71	$178.70	$178.70
Purchase #5	$248.67	10.874%	$275.7104	$275.71	$275.70	$275.70
Purchase #6	$55.58	6.695%	$59.3011	$59.30	$59.30	$59.30
Purchase #7	$221.98	8.496%	$240.8394	$240.84	$240.85	$240.80
7 purchase totals =	$1,054.53		$1,145.9611	$1,145.95	$1,145.95	$1,145.90