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	$247.72	5.585%	$261.5552	$261.56	$261.55	$261.60
Purchase #2	$80.89	11.826%	$90.4561	$90.46	$90.45	$90.50
Purchase #3	$155.53	10.608%	$172.0286	$172.03	$172.05	$172.00
Purchase #4	$152.74	6.585%	$162.7979	$162.80	$162.80	$162.80
Purchase #5	$52.54	10.872%	$58.2521	$58.25	$58.25	$58.30
Purchase #6	$144.36	6.757%	$154.1144	$154.11	$154.10	$154.10
Purchase #7	$98.64	6.295%	$104.8494	$104.85	$104.85	$104.80
7 purchase totals =	$932.42		$1,004.0537	$1,004.06	$1,004.05	$1,004.10