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	$106.60	7.104%	$114.1729	$114.17	$114.15	$114.20
Purchase #2	$37.83	13.381%	$42.892	$42.89	$42.90	$42.90
Purchase #3	$17.64	11.845%	$19.7295	$19.73	$19.75	$19.70
Purchase #4	$119.34	12.368%	$134.1	$134.10	$134.10	$134.10
Purchase #5	$38.79	11.643%	$43.3063	$43.31	$43.30	$43.30
Purchase #6	$79.74	12.548%	$89.7458	$89.75	$89.75	$89.70
Purchase #7	$243.61	12.261%	$273.479	$273.48	$273.50	$273.50
7 purchase totals =	$643.55		$717.4255	$717.43	$717.45	$717.40