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	$43.38	6.223%	$46.0795	$46.08	$46.10	$46.10
Purchase #2	$212.51	5.604%	$224.4191	$224.42	$224.40	$224.40
Purchase #3	$140.89	7.136%	$150.9439	$150.94	$150.95	$150.90
Purchase #4	$96.34	7.315%	$103.3873	$103.39	$103.40	$103.40
Purchase #5	$95.62	11.716%	$106.8228	$106.82	$106.80	$106.80
Purchase #6	$184.33	13.845%	$209.8505	$209.85	$209.85	$209.90
Purchase #7	$247.76	8.280%	$268.2745	$268.27	$268.25	$268.30
7 purchase totals =	$1,020.83		$1,109.7776	$1,109.77	$1,109.75	$1,109.80