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	$239.27	10.304%	$263.9244	$263.92	$263.90	$263.90
Purchase #2	$47.36	11.694%	$52.8983	$52.90	$52.90	$52.90
Purchase #3	$199.49	12.502%	$224.4302	$224.43	$224.45	$224.40
Purchase #4	$166.40	13.219%	$188.3964	$188.40	$188.40	$188.40
Purchase #5	$201.83	8.460%	$218.9048	$218.90	$218.90	$218.90
Purchase #6	$65.52	8.404%	$71.0263	$71.03	$71.05	$71.00
Purchase #7	$130.94	10.473%	$144.6533	$144.65	$144.65	$144.70
7 purchase totals =	$1,050.81		$1,164.2337	$1,164.23	$1,164.25	$1,164.20