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	$185.28	11.477%	$206.5446	$206.54	$206.55	$206.50
Purchase #2	$91.94	8.701%	$99.9397	$99.94	$99.95	$99.90
Purchase #3	$219.74	8.507%	$238.4333	$238.43	$238.45	$238.40
Purchase #4	$41.39	3.657%	$42.9036	$42.90	$42.90	$42.90
Purchase #5	$65.96	10.629%	$72.9709	$72.97	$72.95	$73.00
Purchase #6	$116.65	5.560%	$123.1357	$123.14	$123.15	$123.10
Purchase #7	$250.61	6.422%	$266.7042	$266.70	$266.70	$266.70
7 purchase totals =	$971.57		$1,050.6320	$1,050.62	$1,050.65	$1,050.50