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	$86.91	3.626%	$90.0614	$90.06	$90.05	$90.10
Purchase #2	$173.50	4.471%	$181.2572	$181.26	$181.25	$181.30
Purchase #3	$184.71	4.834%	$193.6389	$193.64	$193.65	$193.60
Purchase #4	$172.66	6.381%	$183.6774	$183.68	$183.70	$183.70
Purchase #5	$98.26	11.432%	$109.4931	$109.49	$109.50	$109.50
Purchase #6	$179.84	11.550%	$200.6115	$200.61	$200.60	$200.60
Purchase #7	$91.97	7.310%	$98.693	$98.69	$98.70	$98.70
7 purchase totals =	$987.85		$1,057.4325	$1,057.43	$1,057.45	$1,057.50