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	$153.74	7.685%	$165.5549	$165.55	$165.55	$165.60
Purchase #2	$100.47	3.354%	$103.8398	$103.84	$103.85	$103.80
Purchase #3	$79.89	12.431%	$89.8211	$89.82	$89.80	$89.80
Purchase #4	$115.91	13.693%	$131.7816	$131.78	$131.80	$131.80
Purchase #5	$173.68	5.132%	$182.5933	$182.59	$182.60	$182.60
Purchase #6	$236.83	5.220%	$249.1925	$249.19	$249.20	$249.20
Purchase #7	$200.66	6.460%	$213.6226	$213.62	$213.60	$213.60
7 purchase totals =	$1,061.18		$1,136.4058	$1,136.39	$1,136.40	$1,136.40