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	$158.80	5.843%	$168.0787	$168.08	$168.10	$168.10
Purchase #2	$82.30	9.502%	$90.1201	$90.12	$90.10	$90.10
Purchase #3	$67.53	13.295%	$76.5081	$76.51	$76.50	$76.50
Purchase #4	$190.74	13.555%	$216.5948	$216.59	$216.60	$216.60
Purchase #5	$142.96	3.532%	$148.0093	$148.01	$148.00	$148.00
Purchase #6	$120.49	3.200%	$124.3457	$124.35	$124.35	$124.30
Purchase #7	$161.40	10.676%	$178.6311	$178.63	$178.65	$178.60
7 purchase totals =	$924.22		$1,002.2878	$1,002.29	$1,002.30	$1,002.20