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	$226.71	3.366%	$234.3411	$234.34	$234.35	$234.30
Purchase #2	$10.27	3.107%	$10.5891	$10.59	$10.60	$10.60
Purchase #3	$176.45	6.866%	$188.5651	$188.57	$188.55	$188.60
Purchase #4	$105.72	11.169%	$117.5279	$117.53	$117.55	$117.50
Purchase #5	$187.98	6.267%	$199.7607	$199.76	$199.75	$199.80
Purchase #6	$115.92	9.798%	$127.2778	$127.28	$127.30	$127.30
Purchase #7	$79.94	11.827%	$89.3945	$89.39	$89.40	$89.40
7 purchase totals =	$902.99		$967.4562	$967.46	$967.50	$967.50