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	$132.32	13.629%	$150.3539	$150.35	$150.35	$150.40
Purchase #2	$92.53	10.360%	$102.1161	$102.12	$102.10	$102.10
Purchase #3	$94.64	6.499%	$100.7907	$100.79	$100.80	$100.80
Purchase #4	$97.65	6.838%	$104.3273	$104.33	$104.35	$104.30
Purchase #5	$132.93	7.476%	$142.8678	$142.87	$142.85	$142.90
Purchase #6	$96.79	4.163%	$100.8194	$100.82	$100.80	$100.80
Purchase #7	$74.79	12.158%	$83.883	$83.88	$83.90	$83.90
7 purchase totals =	$721.65		$785.1582	$785.16	$785.15	$785.20