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	$194.31	3.328%	$200.7766	$200.78	$200.80	$200.80
Purchase #2	$55.62	4.170%	$57.9394	$57.94	$57.95	$57.90
Purchase #3	$149.36	10.172%	$164.5529	$164.55	$164.55	$164.60
Purchase #4	$74.56	4.690%	$78.0569	$78.06	$78.05	$78.10
Purchase #5	$201.96	10.351%	$222.8649	$222.86	$222.85	$222.90
Purchase #6	$59.88	7.251%	$64.2219	$64.22	$64.20	$64.20
Purchase #7	$54.43	6.628%	$58.0376	$58.04	$58.05	$58.00
7 purchase totals =	$790.12		$846.4502	$846.45	$846.45	$846.50