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	$110.77	11.590%	$123.6082	$123.61	$123.60	$123.60
Purchase #2	$171.45	8.350%	$185.7661	$185.77	$185.75	$185.80
Purchase #3	$178.41	3.548%	$184.74	$184.74	$184.75	$184.70
Purchase #4	$192.29	10.216%	$211.9343	$211.93	$211.95	$211.90
Purchase #5	$247.67	8.510%	$268.7467	$268.75	$268.75	$268.70
Purchase #6	$242.88	8.495%	$263.5127	$263.51	$263.50	$263.50
Purchase #7	$196.81	4.423%	$205.5149	$205.51	$205.50	$205.50
7 purchase totals =	$1,340.28		$1,443.8229	$1,443.82	$1,443.80	$1,443.70