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	$141.96	7.677%	$152.8583	$152.86	$152.85	$152.90
Purchase #2	$30.55	7.752%	$32.9182	$32.92	$32.90	$32.90
Purchase #3	$165.95	11.339%	$184.7671	$184.77	$184.75	$184.80
Purchase #4	$66.99	7.678%	$72.1335	$72.13	$72.15	$72.10
Purchase #5	$65.66	9.805%	$72.098	$72.10	$72.10	$72.10
Purchase #6	$95.44	9.271%	$104.2882	$104.29	$104.30	$104.30
Purchase #7	$25.74	10.715%	$28.498	$28.50	$28.50	$28.50
7 purchase totals =	$592.29		$647.5613	$647.57	$647.55	$647.60