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	$219.28	4.228%	$228.5512	$228.55	$228.55	$228.60
Purchase #2	$103.69	10.759%	$114.846	$114.85	$114.85	$114.80
Purchase #3	$101.57	3.270%	$104.8913	$104.89	$104.90	$104.90
Purchase #4	$180.83	12.399%	$203.2511	$203.25	$203.25	$203.30
Purchase #5	$75.51	13.801%	$85.9311	$85.93	$85.95	$85.90
Purchase #6	$43.65	5.457%	$46.032	$46.03	$46.05	$46.00
Purchase #7	$96.87	10.374%	$106.9193	$106.92	$106.90	$106.90
7 purchase totals =	$821.40		$890.4220	$890.42	$890.45	$890.40