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	$130.78	8.778%	$142.2599	$142.26	$142.25	$142.30
Purchase #2	$58.94	11.410%	$65.6651	$65.67	$65.65	$65.70
Purchase #3	$38.87	6.752%	$41.4945	$41.49	$41.50	$41.50
Purchase #4	$101.56	12.767%	$114.5262	$114.53	$114.55	$114.50
Purchase #5	$202.85	12.336%	$227.8736	$227.87	$227.85	$227.90
Purchase #6	$245.51	7.167%	$263.1057	$263.11	$263.10	$263.10
Purchase #7	$153.91	6.773%	$164.3343	$164.33	$164.35	$164.30
7 purchase totals =	$932.42		$1,019.2593	$1,019.26	$1,019.25	$1,019.30