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	$143.95	13.442%	$163.2998	$163.30	$163.30	$163.30
Purchase #2	$51.68	5.537%	$54.5415	$54.54	$54.55	$54.50
Purchase #3	$28.33	7.595%	$30.4817	$30.48	$30.50	$30.50
Purchase #4	$148.40	13.817%	$168.9044	$168.90	$168.90	$168.90
Purchase #5	$138.40	7.261%	$148.4492	$148.45	$148.45	$148.40
Purchase #6	$56.38	8.751%	$61.3138	$61.31	$61.30	$61.30
Purchase #7	$127.28	9.716%	$139.6465	$139.65	$139.65	$139.60
7 purchase totals =	$694.42		$766.6369	$766.63	$766.65	$766.50