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	$25.97	4.365%	$27.1036	$27.10	$27.10	$27.10
Purchase #2	$130.54	5.107%	$137.2067	$137.21	$137.20	$137.20
Purchase #3	$233.62	5.141%	$245.6304	$245.63	$245.65	$245.60
Purchase #4	$90.87	4.844%	$95.2717	$95.27	$95.25	$95.30
Purchase #5	$99.79	10.337%	$110.1053	$110.11	$110.10	$110.10
Purchase #6	$102.74	13.650%	$116.764	$116.76	$116.75	$116.80
Purchase #7	$82.47	9.664%	$90.4399	$90.44	$90.45	$90.40
7 purchase totals =	$766.00		$822.5216	$822.52	$822.50	$822.50