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	$145.89	12.692%	$164.4064	$164.41	$164.40	$164.40
Purchase #2	$58.51	8.283%	$63.3564	$63.36	$63.35	$63.40
Purchase #3	$163.81	11.444%	$182.5564	$182.56	$182.55	$182.60
Purchase #4	$86.83	4.682%	$90.8954	$90.90	$90.90	$90.90
Purchase #5	$95.43	8.633%	$103.6685	$103.67	$103.65	$103.70
Purchase #6	$174.40	6.740%	$186.1546	$186.15	$186.15	$186.20
Purchase #7	$211.52	7.754%	$227.9213	$227.92	$227.90	$227.90
7 purchase totals =	$936.39		$1,018.9590	$1,018.97	$1,018.90	$1,019.10