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	$163.32	11.401%	$181.9401	$181.94	$181.95	$181.90
Purchase #2	$152.84	10.298%	$168.5795	$168.58	$168.60	$168.60
Purchase #3	$215.48	4.610%	$225.4136	$225.41	$225.40	$225.40
Purchase #4	$89.81	10.480%	$99.2221	$99.22	$99.20	$99.20
Purchase #5	$207.43	12.655%	$233.6803	$233.68	$233.70	$233.70
Purchase #6	$5.31	5.437%	$5.5987	$5.60	$5.60	$5.60
Purchase #7	$247.36	6.673%	$263.8663	$263.87	$263.85	$263.90
7 purchase totals =	$1,081.55		$1,178.3006	$1,178.30	$1,178.30	$1,178.30