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	$84.72	5.727%	$89.5719	$89.57	$89.55	$89.60
Purchase #2	$12.67	12.487%	$14.2521	$14.25	$14.25	$14.30
Purchase #3	$22.61	10.570%	$24.9999	$25.00	$25.00	$25.00
Purchase #4	$85.96	6.228%	$91.3136	$91.31	$91.30	$91.30
Purchase #5	$57.75	11.398%	$64.3323	$64.33	$64.35	$64.30
Purchase #6	$50.49	6.693%	$53.8693	$53.87	$53.85	$53.90
Purchase #7	$129.49	9.717%	$142.0725	$142.07	$142.05	$142.10
7 purchase totals =	$443.69		$480.4116	$480.40	$480.35	$480.50