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	$165.81	13.291%	$187.8478	$187.85	$187.85	$187.80
Purchase #2	$97.28	12.331%	$109.2756	$109.28	$109.30	$109.30
Purchase #3	$70.92	3.637%	$73.4994	$73.50	$73.50	$73.50
Purchase #4	$35.55	6.246%	$37.7705	$37.77	$37.75	$37.80
Purchase #5	$159.82	5.443%	$168.519	$168.52	$168.50	$168.50
Purchase #6	$84.67	9.582%	$92.7831	$92.78	$92.80	$92.80
Purchase #7	$59.26	3.578%	$61.3803	$61.38	$61.40	$61.40
7 purchase totals =	$673.31		$731.0757	$731.08	$731.10	$731.10