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	$69.78	3.475%	$72.2049	$72.20	$72.20	$72.20
Purchase #2	$76.46	8.658%	$83.0799	$83.08	$83.10	$83.10
Purchase #3	$93.32	8.836%	$101.5658	$101.57	$101.55	$101.60
Purchase #4	$179.31	11.784%	$200.4399	$200.44	$200.45	$200.40
Purchase #5	$66.72	5.124%	$70.1387	$70.14	$70.15	$70.10
Purchase #6	$176.49	4.333%	$184.1373	$184.14	$184.15	$184.10
Purchase #7	$69.63	4.530%	$72.7842	$72.78	$72.80	$72.80
7 purchase totals =	$731.71		$784.3507	$784.35	$784.40	$784.30