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	$173.78	9.549%	$190.3743	$190.37	$190.35	$190.40
Purchase #2	$168.80	3.545%	$174.784	$174.78	$174.80	$174.80
Purchase #3	$85.47	6.560%	$91.0768	$91.08	$91.10	$91.10
Purchase #4	$110.52	13.292%	$125.2103	$125.21	$125.20	$125.20
Purchase #5	$165.72	12.225%	$185.9793	$185.98	$186.00	$186.00
Purchase #6	$53.66	13.849%	$61.0914	$61.09	$61.10	$61.10
Purchase #7	$77.87	5.862%	$82.4347	$82.43	$82.45	$82.40
7 purchase totals =	$835.82		$910.9508	$910.94	$911.00	$911.00