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	$128.73	9.794%	$141.3378	$141.34	$141.35	$141.30
Purchase #2	$48.96	13.472%	$55.5559	$55.56	$55.55	$55.60
Purchase #3	$73.44	6.468%	$78.1901	$78.19	$78.20	$78.20
Purchase #4	$173.65	4.374%	$181.2455	$181.25	$181.25	$181.20
Purchase #5	$156.34	13.818%	$177.9431	$177.94	$177.95	$177.90
Purchase #6	$139.86	3.477%	$144.7229	$144.72	$144.70	$144.70
Purchase #7	$51.36	4.153%	$53.493	$53.49	$53.50	$53.50
7 purchase totals =	$772.34		$832.4883	$832.49	$832.50	$832.40