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	$214.85	6.535%	$228.8904	$228.89	$228.90	$228.90
Purchase #2	$181.53	7.798%	$195.6857	$195.69	$195.70	$195.70
Purchase #3	$125.46	4.506%	$131.1132	$131.11	$131.10	$131.10
Purchase #4	$130.34	6.769%	$139.1627	$139.16	$139.15	$139.20
Purchase #5	$75.61	6.127%	$80.2426	$80.24	$80.25	$80.20
Purchase #6	$122.91	3.435%	$127.132	$127.13	$127.15	$127.10
Purchase #7	$130.83	8.272%	$141.6523	$141.65	$141.65	$141.70
7 purchase totals =	$981.53		$1,043.8789	$1,043.87	$1,043.90	$1,043.90