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	$143.41	8.700%	$155.8867	$155.89	$155.90	$155.90
Purchase #2	$51.71	3.765%	$53.6569	$53.66	$53.65	$53.70
Purchase #3	$228.63	13.428%	$259.3304	$259.33	$259.35	$259.30
Purchase #4	$101.27	11.475%	$112.8907	$112.89	$112.90	$112.90
Purchase #5	$59.68	5.808%	$63.1462	$63.15	$63.15	$63.10
Purchase #6	$73.35	3.469%	$75.8945	$75.89	$75.90	$75.90
Purchase #7	$38.77	11.525%	$43.2382	$43.24	$43.25	$43.20
7 purchase totals =	$696.82		$764.0436	$764.05	$764.10	$764.00