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	$77.81	12.538%	$87.5658	$87.57	$87.55	$87.60
Purchase #2	$191.37	4.629%	$200.2285	$200.23	$200.25	$200.20
Purchase #3	$95.42	9.327%	$104.3198	$104.32	$104.30	$104.30
Purchase #4	$172.92	3.121%	$178.3168	$178.32	$178.30	$178.30
Purchase #5	$244.68	11.629%	$273.1338	$273.13	$273.15	$273.10
Purchase #6	$83.39	7.247%	$89.4333	$89.43	$89.45	$89.40
Purchase #7	$211.28	7.226%	$226.5471	$226.55	$226.55	$226.50
7 purchase totals =	$1,076.87		$1,159.5451	$1,159.55	$1,159.55	$1,159.40