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	$205.52	3.221%	$212.1398	$212.14	$212.15	$212.10
Purchase #2	$167.89	12.287%	$188.5186	$188.52	$188.50	$188.50
Purchase #3	$245.53	4.597%	$256.817	$256.82	$256.80	$256.80
Purchase #4	$12.92	4.329%	$13.4793	$13.48	$13.50	$13.50
Purchase #5	$49.32	3.136%	$50.8667	$50.87	$50.85	$50.90
Purchase #6	$93.68	5.496%	$98.8287	$98.83	$98.85	$98.80
Purchase #7	$91.87	11.789%	$102.7006	$102.70	$102.70	$102.70
7 purchase totals =	$866.73		$923.3507	$923.36	$923.35	$923.30