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	$183.88	4.456%	$192.0737	$192.07	$192.05	$192.10
Purchase #2	$197.40	9.216%	$215.5924	$215.59	$215.60	$215.60
Purchase #3	$179.96	11.360%	$200.4035	$200.40	$200.40	$200.40
Purchase #4	$209.82	13.693%	$238.5507	$238.55	$238.55	$238.60
Purchase #5	$28.55	4.111%	$29.7237	$29.72	$29.70	$29.70
Purchase #6	$44.40	13.440%	$50.3674	$50.37	$50.35	$50.40
Purchase #7	$72.40	13.164%	$81.9307	$81.93	$81.95	$81.90
7 purchase totals =	$916.41		$1,008.6421	$1,008.63	$1,008.60	$1,008.70