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	$157.44	9.708%	$172.7243	$172.72	$172.70	$172.70
Purchase #2	$187.74	4.817%	$196.7834	$196.78	$196.80	$196.80
Purchase #3	$88.82	6.424%	$94.5258	$94.53	$94.55	$94.50
Purchase #4	$149.75	9.863%	$164.5198	$164.52	$164.50	$164.50
Purchase #5	$127.90	4.786%	$134.0213	$134.02	$134.00	$134.00
Purchase #6	$85.76	12.373%	$96.3711	$96.37	$96.35	$96.40
Purchase #7	$127.62	8.414%	$138.3579	$138.36	$138.35	$138.40
7 purchase totals =	$925.03		$997.3036	$997.30	$997.25	$997.30