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	$143.41	10.831%	$158.9427	$158.94	$158.95	$158.90
Purchase #2	$100.94	8.830%	$109.853	$109.85	$109.85	$109.90
Purchase #3	$35.82	6.356%	$38.0967	$38.10	$38.10	$38.10
Purchase #4	$232.55	4.813%	$243.7426	$243.74	$243.75	$243.70
Purchase #5	$148.72	10.386%	$164.1661	$164.17	$164.15	$164.20
Purchase #6	$35.67	4.773%	$37.3725	$37.37	$37.35	$37.40
Purchase #7	$167.92	9.542%	$183.9429	$183.94	$183.95	$183.90
7 purchase totals =	$865.03		$936.1165	$936.11	$936.10	$936.10