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	$14.57	3.244%	$15.0427	$15.04	$15.05	$15.00
Purchase #2	$164.88	10.723%	$182.5601	$182.56	$182.55	$182.60
Purchase #3	$175.44	9.608%	$192.2963	$192.30	$192.30	$192.30
Purchase #4	$239.98	13.135%	$271.5014	$271.50	$271.50	$271.50
Purchase #5	$91.79	4.186%	$95.6323	$95.63	$95.65	$95.60
Purchase #6	$168.26	12.272%	$188.9089	$188.91	$188.90	$188.90
Purchase #7	$57.76	3.106%	$59.554	$59.55	$59.55	$59.60
7 purchase totals =	$912.68		$1,005.4957	$1,005.49	$1,005.50	$1,005.50