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	$246.72	7.461%	$265.1278	$265.13	$265.15	$265.10
Purchase #2	$101.97	7.524%	$109.6422	$109.64	$109.65	$109.60
Purchase #3	$182.59	7.318%	$195.9519	$195.95	$195.95	$196.00
Purchase #4	$150.44	6.257%	$159.853	$159.85	$159.85	$159.90
Purchase #5	$28.70	9.681%	$31.4784	$31.48	$31.50	$31.50
Purchase #6	$187.50	4.544%	$196.02	$196.02	$196.00	$196.00
Purchase #7	$29.92	10.407%	$33.0338	$33.03	$33.05	$33.00
7 purchase totals =	$927.84		$991.1071	$991.10	$991.15	$991.10