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	$142.69	5.347%	$150.3196	$150.32	$150.30	$150.30
Purchase #2	$59.88	6.530%	$63.7902	$63.79	$63.80	$63.80
Purchase #3	$138.91	6.449%	$147.8683	$147.87	$147.85	$147.90
Purchase #4	$226.58	9.458%	$248.0099	$248.01	$248.00	$248.00
Purchase #5	$245.53	3.792%	$254.8405	$254.84	$254.85	$254.80
Purchase #6	$105.91	5.583%	$111.823	$111.82	$111.80	$111.80
Purchase #7	$73.77	13.386%	$83.6449	$83.64	$83.65	$83.60
7 purchase totals =	$993.27		$1,060.2964	$1,060.29	$1,060.25	$1,060.20