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	$211.64	12.869%	$238.876	$238.88	$238.90	$238.90
Purchase #2	$78.69	8.822%	$85.632	$85.63	$85.65	$85.60
Purchase #3	$26.37	10.695%	$29.1903	$29.19	$29.20	$29.20
Purchase #4	$41.55	12.839%	$46.8846	$46.88	$46.90	$46.90
Purchase #5	$92.97	4.152%	$96.8301	$96.83	$96.85	$96.80
Purchase #6	$236.94	6.421%	$252.1539	$252.15	$252.15	$252.20
Purchase #7	$104.56	7.573%	$112.4783	$112.48	$112.50	$112.50
7 purchase totals =	$792.72		$862.0452	$862.04	$862.15	$862.10