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	$157.36	6.432%	$167.4814	$167.48	$167.50	$167.50
Purchase #2	$234.92	4.433%	$245.334	$245.33	$245.35	$245.30
Purchase #3	$25.87	6.641%	$27.588	$27.59	$27.60	$27.60
Purchase #4	$194.83	7.674%	$209.7813	$209.78	$209.80	$209.80
Purchase #5	$171.25	5.207%	$180.167	$180.17	$180.15	$180.20
Purchase #6	$137.46	3.182%	$141.834	$141.83	$141.85	$141.80
Purchase #7	$161.91	11.866%	$181.1222	$181.12	$181.10	$181.10
7 purchase totals =	$1,083.60		$1,153.3079	$1,153.30	$1,153.35	$1,153.30