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	$48.64	11.640%	$54.3017	$54.30	$54.30	$54.30
Purchase #2	$169.98	4.867%	$178.2529	$178.25	$178.25	$178.30
Purchase #3	$227.98	3.228%	$235.3392	$235.34	$235.35	$235.30
Purchase #4	$245.57	7.339%	$263.5924	$263.59	$263.60	$263.60
Purchase #5	$39.55	9.229%	$43.2001	$43.20	$43.20	$43.20
Purchase #6	$76.30	4.249%	$79.542	$79.54	$79.55	$79.50
Purchase #7	$209.52	6.415%	$222.9607	$222.96	$222.95	$223.00
7 purchase totals =	$1,017.54		$1,077.1890	$1,077.18	$1,077.20	$1,077.20