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	$160.27	6.813%	$171.1892	$171.19	$171.20	$171.20
Purchase #2	$72.69	7.609%	$78.221	$78.22	$78.20	$78.20
Purchase #3	$62.97	7.315%	$67.5763	$67.58	$67.60	$67.60
Purchase #4	$116.33	10.311%	$128.3248	$128.32	$128.30	$128.30
Purchase #5	$206.51	7.708%	$222.4278	$222.43	$222.45	$222.40
Purchase #6	$144.86	3.206%	$149.5042	$149.50	$149.50	$149.50
Purchase #7	$27.82	5.348%	$29.3078	$29.31	$29.30	$29.30
7 purchase totals =	$791.45		$846.5511	$846.55	$846.55	$846.50