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	$158.96	8.379%	$172.2793	$172.28	$172.30	$172.30
Purchase #2	$70.89	4.655%	$74.1899	$74.19	$74.20	$74.20
Purchase #3	$225.48	10.364%	$248.8487	$248.85	$248.85	$248.80
Purchase #4	$197.27	13.354%	$223.6134	$223.61	$223.60	$223.60
Purchase #5	$104.57	4.627%	$109.4085	$109.41	$109.40	$109.40
Purchase #6	$107.77	4.301%	$112.4052	$112.41	$112.40	$112.40
Purchase #7	$98.41	13.449%	$111.6452	$111.65	$111.65	$111.60
7 purchase totals =	$963.35		$1,052.3902	$1,052.40	$1,052.40	$1,052.30