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	$193.28	13.568%	$219.5042	$219.50	$219.50	$219.50
Purchase #2	$109.84	12.765%	$123.8611	$123.86	$123.85	$123.90
Purchase #3	$247.78	8.264%	$268.2565	$268.26	$268.25	$268.30
Purchase #4	$233.34	11.321%	$259.7564	$259.76	$259.75	$259.80
Purchase #5	$71.76	11.861%	$80.2715	$80.27	$80.25	$80.30
Purchase #6	$36.41	7.259%	$39.053	$39.05	$39.05	$39.10
Purchase #7	$59.37	8.805%	$64.5975	$64.60	$64.60	$64.60
7 purchase totals =	$951.78		$1,055.3002	$1,055.30	$1,055.25	$1,055.50