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	$150.43	9.379%	$164.5388	$164.54	$164.55	$164.50
Purchase #2	$92.87	5.490%	$97.9686	$97.97	$97.95	$98.00
Purchase #3	$142.34	12.325%	$159.8834	$159.88	$159.90	$159.90
Purchase #4	$166.33	9.318%	$181.8286	$181.83	$181.85	$181.80
Purchase #5	$168.44	10.106%	$185.4625	$185.46	$185.45	$185.50
Purchase #6	$99.77	6.540%	$106.295	$106.30	$106.30	$106.30
Purchase #7	$109.97	3.755%	$114.0994	$114.10	$114.10	$114.10
7 purchase totals =	$930.15		$1,010.0763	$1,010.08	$1,010.10	$1,010.10