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	$80.51	9.161%	$87.8855	$87.89	$87.90	$87.90
Purchase #2	$91.35	8.780%	$99.3705	$99.37	$99.35	$99.40
Purchase #3	$42.34	13.712%	$48.1457	$48.15	$48.15	$48.10
Purchase #4	$82.65	11.334%	$92.0176	$92.02	$92.00	$92.00
Purchase #5	$19.29	10.187%	$21.2551	$21.26	$21.25	$21.30
Purchase #6	$49.82	4.608%	$52.1157	$52.12	$52.10	$52.10
Purchase #7	$79.33	11.577%	$88.514	$88.51	$88.50	$88.50
7 purchase totals =	$445.29		$489.3041	$489.32	$489.25	$489.30