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	$196.89	6.362%	$209.4161	$209.42	$209.40	$209.40
Purchase #2	$163.88	5.312%	$172.5853	$172.59	$172.60	$172.60
Purchase #3	$31.61	3.473%	$32.7078	$32.71	$32.70	$32.70
Purchase #4	$59.70	5.608%	$63.048	$63.05	$63.05	$63.00
Purchase #5	$112.83	7.438%	$121.2223	$121.22	$121.20	$121.20
Purchase #6	$125.55	4.276%	$130.9185	$130.92	$130.90	$130.90
Purchase #7	$133.56	12.751%	$150.5902	$150.59	$150.60	$150.60
7 purchase totals =	$824.02		$880.4882	$880.50	$880.45	$880.40