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	$36.72	3.114%	$37.8635	$37.86	$37.85	$37.90
Purchase #2	$64.41	11.865%	$72.0522	$72.05	$72.05	$72.10
Purchase #3	$73.61	7.757%	$79.3199	$79.32	$79.30	$79.30
Purchase #4	$154.91	10.735%	$171.5396	$171.54	$171.55	$171.50
Purchase #5	$204.31	13.333%	$231.5507	$231.55	$231.55	$231.60
Purchase #6	$99.60	13.503%	$113.049	$113.05	$113.05	$113.00
Purchase #7	$126.65	4.524%	$132.3796	$132.38	$132.40	$132.40
7 purchase totals =	$760.21		$837.7545	$837.75	$837.75	$837.80