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	$148.50	3.528%	$153.7391	$153.74	$153.75	$153.70
Purchase #2	$154.89	3.834%	$160.8285	$160.83	$160.85	$160.80
Purchase #3	$94.91	3.296%	$98.0382	$98.04	$98.05	$98.00
Purchase #4	$70.61	8.290%	$76.4636	$76.46	$76.45	$76.50
Purchase #5	$248.65	7.798%	$268.0397	$268.04	$268.05	$268.00
Purchase #6	$213.70	13.400%	$242.3358	$242.34	$242.35	$242.30
Purchase #7	$89.44	11.697%	$99.9018	$99.90	$99.90	$99.90
7 purchase totals =	$1,020.70		$1,099.3467	$1,099.35	$1,099.40	$1,099.20