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	$148.37	11.380%	$165.2545	$165.25	$165.25	$165.30
Purchase #2	$46.25	8.743%	$50.2936	$50.29	$50.30	$50.30
Purchase #3	$92.45	13.803%	$105.2109	$105.21	$105.20	$105.20
Purchase #4	$211.31	10.212%	$232.889	$232.89	$232.90	$232.90
Purchase #5	$97.69	12.425%	$109.828	$109.83	$109.85	$109.80
Purchase #6	$23.82	5.403%	$25.107	$25.11	$25.10	$25.10
Purchase #7	$53.30	5.712%	$56.3445	$56.34	$56.35	$56.30
7 purchase totals =	$673.19		$744.9275	$744.92	$744.95	$744.90