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	$144.81	5.855%	$153.2886	$153.29	$153.30	$153.30
Purchase #2	$192.62	4.123%	$200.5617	$200.56	$200.55	$200.60
Purchase #3	$108.34	7.370%	$116.3247	$116.32	$116.30	$116.30
Purchase #4	$152.91	12.735%	$172.3831	$172.38	$172.40	$172.40
Purchase #5	$72.99	11.572%	$81.4364	$81.44	$81.45	$81.40
Purchase #6	$79.57	7.427%	$85.4797	$85.48	$85.50	$85.50
Purchase #7	$167.30	11.248%	$186.1179	$186.12	$186.10	$186.10
7 purchase totals =	$918.54		$995.5921	$995.59	$995.60	$995.60