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	$168.73	9.147%	$184.1637	$184.16	$184.15	$184.20
Purchase #2	$234.30	12.446%	$263.461	$263.46	$263.45	$263.50
Purchase #3	$54.75	4.262%	$57.0834	$57.08	$57.10	$57.10
Purchase #4	$242.37	4.808%	$254.0231	$254.02	$254.00	$254.00
Purchase #5	$174.82	3.835%	$181.5243	$181.52	$181.50	$181.50
Purchase #6	$20.64	13.283%	$23.3816	$23.38	$23.40	$23.40
Purchase #7	$82.61	11.195%	$91.8582	$91.86	$91.85	$91.90
7 purchase totals =	$978.22		$1,055.4953	$1,055.48	$1,055.45	$1,055.60