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	$171.92	5.379%	$181.1676	$181.17	$181.15	$181.20
Purchase #2	$138.98	8.106%	$150.2457	$150.25	$150.25	$150.20
Purchase #3	$140.51	8.405%	$152.3199	$152.32	$152.30	$152.30
Purchase #4	$35.61	6.300%	$37.8534	$37.85	$37.85	$37.90
Purchase #5	$181.25	12.139%	$203.2519	$203.25	$203.25	$203.30
Purchase #6	$86.72	13.304%	$98.2572	$98.26	$98.25	$98.30
Purchase #7	$231.84	11.108%	$257.5928	$257.59	$257.60	$257.60
7 purchase totals =	$986.83		$1,080.6885	$1,080.69	$1,080.65	$1,080.80