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	$178.48	5.230%	$187.8145	$187.81	$187.80	$187.80
Purchase #2	$167.37	11.156%	$186.0418	$186.04	$186.05	$186.00
Purchase #3	$163.53	7.303%	$175.4726	$175.47	$175.45	$175.50
Purchase #4	$220.52	13.787%	$250.9231	$250.92	$250.90	$250.90
Purchase #5	$100.83	4.292%	$105.1576	$105.16	$105.15	$105.20
Purchase #6	$250.62	9.865%	$275.3437	$275.34	$275.35	$275.30
Purchase #7	$122.39	7.486%	$131.5521	$131.55	$131.55	$131.60
7 purchase totals =	$1,203.74		$1,312.3054	$1,312.29	$1,312.25	$1,312.30