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	$24.50	4.844%	$25.6868	$25.69	$25.70	$25.70
Purchase #2	$82.49	10.297%	$90.984	$90.98	$91.00	$91.00
Purchase #3	$196.62	11.144%	$218.5313	$218.53	$218.55	$218.50
Purchase #4	$42.40	6.408%	$45.117	$45.12	$45.10	$45.10
Purchase #5	$18.53	10.666%	$20.5064	$20.51	$20.50	$20.50
Purchase #6	$202.79	13.210%	$229.5786	$229.58	$229.60	$229.60
Purchase #7	$18.90	11.245%	$21.0253	$21.03	$21.05	$21.00
7 purchase totals =	$586.23		$651.4294	$651.44	$651.50	$651.40