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	$94.88	5.676%	$100.2654	$100.27	$100.25	$100.30
Purchase #2	$55.41	6.701%	$59.123	$59.12	$59.10	$59.10
Purchase #3	$153.98	3.122%	$158.7873	$158.79	$158.80	$158.80
Purchase #4	$233.34	5.125%	$245.2987	$245.30	$245.30	$245.30
Purchase #5	$211.71	6.312%	$225.0731	$225.07	$225.05	$225.10
Purchase #6	$109.69	12.296%	$123.1775	$123.18	$123.20	$123.20
Purchase #7	$131.92	12.721%	$148.7015	$148.70	$148.70	$148.70
7 purchase totals =	$990.93		$1,060.4265	$1,060.43	$1,060.40	$1,060.50