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	$80.33	7.177%	$86.0953	$86.10	$86.10	$86.10
Purchase #2	$59.48	13.580%	$67.5574	$67.56	$67.55	$67.60
Purchase #3	$43.59	8.773%	$47.4142	$47.41	$47.40	$47.40
Purchase #4	$88.64	13.368%	$100.4894	$100.49	$100.50	$100.50
Purchase #5	$96.70	9.578%	$105.9619	$105.96	$105.95	$106.00
Purchase #6	$102.27	8.427%	$110.8883	$110.89	$110.90	$110.90
Purchase #7	$246.38	9.143%	$268.9065	$268.91	$268.90	$268.90
7 purchase totals =	$717.39		$787.3130	$787.32	$787.30	$787.40