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	$160.74	6.524%	$171.2267	$171.23	$171.25	$171.20
Purchase #2	$226.27	10.102%	$249.1278	$249.13	$249.15	$249.10
Purchase #3	$193.91	13.574%	$220.2313	$220.23	$220.25	$220.20
Purchase #4	$215.89	11.806%	$241.378	$241.38	$241.40	$241.40
Purchase #5	$42.54	13.854%	$48.4335	$48.43	$48.45	$48.40
Purchase #6	$61.85	13.711%	$70.3303	$70.33	$70.35	$70.30
Purchase #7	$154.98	10.757%	$171.6512	$171.65	$171.65	$171.70
7 purchase totals =	$1,056.18		$1,172.3788	$1,172.38	$1,172.50	$1,172.30