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	$126.66	4.122%	$131.8809	$131.88	$131.90	$131.90
Purchase #2	$51.52	3.697%	$53.4247	$53.42	$53.40	$53.40
Purchase #3	$221.58	3.755%	$229.9003	$229.90	$229.90	$229.90
Purchase #4	$155.48	6.744%	$165.9656	$165.97	$165.95	$166.00
Purchase #5	$114.73	3.359%	$118.5838	$118.58	$118.60	$118.60
Purchase #6	$221.75	10.483%	$244.9961	$245.00	$245.00	$245.00
Purchase #7	$30.82	5.610%	$32.549	$32.55	$32.55	$32.50
7 purchase totals =	$922.54		$977.3004	$977.30	$977.30	$977.30