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	$102.29	11.248%	$113.7956	$113.80	$113.80	$113.80
Purchase #2	$56.63	3.151%	$58.4144	$58.41	$58.40	$58.40
Purchase #3	$112.38	13.713%	$127.7907	$127.79	$127.80	$127.80
Purchase #4	$47.36	7.345%	$50.8386	$50.84	$50.85	$50.80
Purchase #5	$153.89	12.206%	$172.6738	$172.67	$172.65	$172.70
Purchase #6	$124.34	3.551%	$128.7553	$128.76	$128.75	$128.80
Purchase #7	$68.93	5.618%	$72.8025	$72.80	$72.80	$72.80
7 purchase totals =	$665.82		$725.0709	$725.07	$725.05	$725.10