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	$156.36	13.128%	$176.8869	$176.89	$176.90	$176.90
Purchase #2	$73.27	8.200%	$79.2781	$79.28	$79.30	$79.30
Purchase #3	$80.41	13.574%	$91.3249	$91.32	$91.30	$91.30
Purchase #4	$141.97	4.442%	$148.2763	$148.28	$148.30	$148.30
Purchase #5	$143.71	6.399%	$152.906	$152.91	$152.90	$152.90
Purchase #6	$57.47	10.479%	$63.4923	$63.49	$63.50	$63.50
Purchase #7	$41.59	13.598%	$47.2454	$47.25	$47.25	$47.20
7 purchase totals =	$694.78		$759.4099	$759.42	$759.45	$759.40