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	$49.67	4.695%	$52.002	$52.00	$52.00	$52.00
Purchase #2	$159.75	4.783%	$167.3908	$167.39	$167.40	$167.40
Purchase #3	$215.86	8.215%	$233.5929	$233.59	$233.60	$233.60
Purchase #4	$221.88	9.231%	$242.3617	$242.36	$242.35	$242.40
Purchase #5	$207.39	9.472%	$227.034	$227.03	$227.05	$227.00
Purchase #6	$184.28	4.621%	$192.7956	$192.80	$192.80	$192.80
Purchase #7	$144.50	11.206%	$160.6927	$160.69	$160.70	$160.70
7 purchase totals =	$1,183.33		$1,275.8697	$1,275.86	$1,275.90	$1,275.90