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	$181.77	6.133%	$192.918	$192.92	$192.90	$192.90
Purchase #2	$98.81	5.607%	$104.3503	$104.35	$104.35	$104.40
Purchase #3	$22.26	12.395%	$25.0191	$25.02	$25.00	$25.00
Purchase #4	$37.47	11.681%	$41.8469	$41.85	$41.85	$41.80
Purchase #5	$103.75	8.216%	$112.2741	$112.27	$112.25	$112.30
Purchase #6	$129.42	12.726%	$145.89	$145.89	$145.90	$145.90
Purchase #7	$120.78	8.781%	$131.3857	$131.39	$131.40	$131.40
7 purchase totals =	$694.26		$753.6841	$753.69	$753.65	$753.70