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	$129.41	10.123%	$142.5102	$142.51	$142.50	$142.50
Purchase #2	$89.83	11.506%	$100.1658	$100.17	$100.15	$100.20
Purchase #3	$121.61	7.126%	$130.2759	$130.28	$130.30	$130.30
Purchase #4	$233.69	3.828%	$242.6357	$242.64	$242.65	$242.60
Purchase #5	$248.27	13.620%	$282.0844	$282.08	$282.10	$282.10
Purchase #6	$183.38	11.770%	$204.9638	$204.96	$204.95	$205.00
Purchase #7	$39.46	5.279%	$41.5431	$41.54	$41.55	$41.50
7 purchase totals =	$1,045.65		$1,144.1789	$1,144.18	$1,144.20	$1,144.20