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	$218.49	12.299%	$245.3621	$245.36	$245.35	$245.40
Purchase #2	$228.72	6.805%	$244.2844	$244.28	$244.30	$244.30
Purchase #3	$168.67	12.846%	$190.3373	$190.34	$190.35	$190.30
Purchase #4	$53.70	4.282%	$55.9994	$56.00	$56.00	$56.00
Purchase #5	$162.67	12.693%	$183.3177	$183.32	$183.30	$183.30
Purchase #6	$47.26	8.137%	$51.1055	$51.11	$51.10	$51.10
Purchase #7	$107.50	3.689%	$111.4657	$111.47	$111.45	$111.50
7 purchase totals =	$987.01		$1,081.8721	$1,081.88	$1,081.85	$1,081.90