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	$148.31	12.490%	$166.8339	$166.83	$166.85	$166.80
Purchase #2	$141.80	5.373%	$149.4189	$149.42	$149.40	$149.40
Purchase #3	$29.76	12.564%	$33.499	$33.50	$33.50	$33.50
Purchase #4	$43.57	8.613%	$47.3227	$47.32	$47.30	$47.30
Purchase #5	$82.94	3.502%	$85.8446	$85.84	$85.85	$85.80
Purchase #6	$132.69	7.439%	$142.5608	$142.56	$142.55	$142.60
Purchase #7	$172.54	5.156%	$181.4362	$181.44	$181.45	$181.40
7 purchase totals =	$751.61		$806.9161	$806.91	$806.90	$806.80