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	$98.39	6.853%	$105.1327	$105.13	$105.15	$105.10
Purchase #2	$51.95	6.263%	$55.2036	$55.20	$55.20	$55.20
Purchase #3	$147.38	3.336%	$152.2966	$152.30	$152.30	$152.30
Purchase #4	$169.82	5.395%	$178.9818	$178.98	$179.00	$179.00
Purchase #5	$111.27	10.504%	$122.9578	$122.96	$122.95	$123.00
Purchase #6	$95.75	4.419%	$99.9812	$99.98	$100.00	$100.00
Purchase #7	$93.78	6.693%	$100.0567	$100.06	$100.05	$100.10
7 purchase totals =	$768.34		$814.6104	$814.61	$814.65	$814.70