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	$157.78	4.404%	$164.7286	$164.73	$164.75	$164.70
Purchase #2	$174.37	12.146%	$195.549	$195.55	$195.55	$195.50
Purchase #3	$248.25	7.360%	$266.5212	$266.52	$266.50	$266.50
Purchase #4	$148.68	12.765%	$167.659	$167.66	$167.65	$167.70
Purchase #5	$118.30	4.559%	$123.6933	$123.69	$123.70	$123.70
Purchase #6	$167.36	7.444%	$179.8183	$179.82	$179.80	$179.80
Purchase #7	$139.49	9.171%	$152.2826	$152.28	$152.30	$152.30
7 purchase totals =	$1,154.23		$1,250.2520	$1,250.25	$1,250.25	$1,250.20