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	$115.76	6.421%	$123.1929	$123.19	$123.20	$123.20
Purchase #2	$118.69	7.540%	$127.6392	$127.64	$127.65	$127.60
Purchase #3	$235.42	4.241%	$245.4042	$245.40	$245.40	$245.40
Purchase #4	$173.52	4.626%	$181.547	$181.55	$181.55	$181.50
Purchase #5	$10.73	11.437%	$11.9572	$11.96	$11.95	$12.00
Purchase #6	$147.57	11.599%	$164.6866	$164.69	$164.70	$164.70
Purchase #7	$153.69	10.460%	$169.766	$169.77	$169.75	$169.80
7 purchase totals =	$955.38		$1,024.1931	$1,024.20	$1,024.20	$1,024.20