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	$150.40	3.800%	$156.1152	$156.12	$156.10	$156.10
Purchase #2	$95.93	4.827%	$100.5605	$100.56	$100.55	$100.60
Purchase #3	$104.33	4.487%	$109.0113	$109.01	$109.00	$109.00
Purchase #4	$25.25	12.221%	$28.3358	$28.34	$28.35	$28.30
Purchase #5	$202.82	11.557%	$226.2599	$226.26	$226.25	$226.30
Purchase #6	$172.67	5.362%	$181.9286	$181.93	$181.95	$181.90
Purchase #7	$232.97	11.242%	$259.1605	$259.16	$259.15	$259.20
7 purchase totals =	$984.37		$1,061.3718	$1,061.38	$1,061.35	$1,061.40