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	$59.30	4.276%	$61.8357	$61.84	$61.85	$61.80
Purchase #2	$74.74	7.824%	$80.5877	$80.59	$80.60	$80.60
Purchase #3	$126.95	10.292%	$140.0157	$140.02	$140.00	$140.00
Purchase #4	$100.79	7.669%	$108.5196	$108.52	$108.50	$108.50
Purchase #5	$218.63	11.618%	$244.0304	$244.03	$244.05	$244.00
Purchase #6	$59.87	9.171%	$65.3607	$65.36	$65.35	$65.40
Purchase #7	$28.28	12.360%	$31.7754	$31.78	$31.80	$31.80
7 purchase totals =	$668.56		$732.1252	$732.14	$732.15	$732.10