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	$71.32	8.139%	$77.1247	$77.12	$77.10	$77.10
Purchase #2	$83.28	7.391%	$89.4352	$89.44	$89.45	$89.40
Purchase #3	$92.41	5.515%	$97.5064	$97.51	$97.50	$97.50
Purchase #4	$166.41	4.850%	$174.4809	$174.48	$174.50	$174.50
Purchase #5	$61.76	7.385%	$66.321	$66.32	$66.30	$66.30
Purchase #6	$136.90	3.749%	$142.0324	$142.03	$142.05	$142.00
Purchase #7	$182.49	10.436%	$201.5347	$201.53	$201.55	$201.50
7 purchase totals =	$794.57		$848.4353	$848.43	$848.45	$848.30