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	$174.59	12.653%	$196.6809	$196.68	$196.70	$196.70
Purchase #2	$230.30	10.858%	$255.306	$255.31	$255.30	$255.30
Purchase #3	$92.80	3.478%	$96.0276	$96.03	$96.05	$96.00
Purchase #4	$159.26	4.205%	$165.9569	$165.96	$165.95	$166.00
Purchase #5	$88.69	8.175%	$95.9404	$95.94	$95.95	$95.90
Purchase #6	$28.62	11.202%	$31.826	$31.83	$31.85	$31.80
Purchase #7	$126.84	3.729%	$131.5699	$131.57	$131.55	$131.60
7 purchase totals =	$901.10		$973.3077	$973.32	$973.35	$973.30