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	$54.49	3.747%	$56.5317	$56.53	$56.55	$56.50
Purchase #2	$54.89	11.350%	$61.12	$61.12	$61.10	$61.10
Purchase #3	$97.36	4.385%	$101.6292	$101.63	$101.65	$101.60
Purchase #4	$244.82	8.484%	$265.5905	$265.59	$265.60	$265.60
Purchase #5	$123.89	10.490%	$136.8861	$136.89	$136.90	$136.90
Purchase #6	$130.67	4.339%	$136.3398	$136.34	$136.35	$136.30
Purchase #7	$22.39	9.163%	$24.4416	$24.44	$24.45	$24.40
7 purchase totals =	$728.51		$782.5389	$782.54	$782.60	$782.40