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	$81.37	12.169%	$91.2719	$91.27	$91.25	$91.30
Purchase #2	$63.34	11.488%	$70.6165	$70.62	$70.60	$70.60
Purchase #3	$82.44	4.206%	$85.9074	$85.91	$85.90	$85.90
Purchase #4	$117.42	13.641%	$133.4373	$133.44	$133.45	$133.40
Purchase #5	$235.52	7.714%	$253.688	$253.69	$253.70	$253.70
Purchase #6	$125.77	12.632%	$141.6573	$141.66	$141.65	$141.70
Purchase #7	$224.41	3.835%	$233.0161	$233.02	$233.00	$233.00
7 purchase totals =	$930.27		$1,009.5945	$1,009.61	$1,009.55	$1,009.60