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	$118.30	7.657%	$127.3582	$127.36	$127.35	$127.40
Purchase #2	$45.66	10.654%	$50.5246	$50.52	$50.50	$50.50
Purchase #3	$41.83	11.119%	$46.4811	$46.48	$46.50	$46.50
Purchase #4	$168.90	7.505%	$181.5759	$181.58	$181.60	$181.60
Purchase #5	$139.44	7.732%	$150.2215	$150.22	$150.20	$150.20
Purchase #6	$26.47	9.358%	$28.9471	$28.95	$28.95	$28.90
Purchase #7	$185.34	5.507%	$195.5467	$195.55	$195.55	$195.50
7 purchase totals =	$725.94		$780.6551	$780.66	$780.65	$780.60