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	$13.36	9.183%	$14.5868	$14.59	$14.60	$14.60
Purchase #2	$144.27	8.456%	$156.4695	$156.47	$156.45	$156.50
Purchase #3	$95.55	4.294%	$99.6529	$99.65	$99.65	$99.70
Purchase #4	$84.56	5.178%	$88.9385	$88.94	$88.95	$88.90
Purchase #5	$62.88	6.769%	$67.1363	$67.14	$67.15	$67.10
Purchase #6	$172.92	8.805%	$188.1456	$188.15	$188.15	$188.10
Purchase #7	$178.47	6.644%	$190.3275	$190.33	$190.35	$190.30
7 purchase totals =	$752.01		$805.2571	$805.27	$805.30	$805.20