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	$119.89	5.294%	$126.237	$126.24	$126.25	$126.20
Purchase #2	$89.36	11.235%	$99.3996	$99.40	$99.40	$99.40
Purchase #3	$239.91	9.812%	$263.45	$263.45	$263.45	$263.50
Purchase #4	$79.80	11.694%	$89.1318	$89.13	$89.15	$89.10
Purchase #5	$167.55	7.735%	$180.51	$180.51	$180.50	$180.50
Purchase #6	$167.29	9.828%	$183.7313	$183.73	$183.75	$183.70
Purchase #7	$71.27	10.533%	$78.7769	$78.78	$78.80	$78.80
7 purchase totals =	$935.07		$1,021.2366	$1,021.24	$1,021.30	$1,021.20