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	$184.77	7.647%	$198.8994	$198.90	$198.90	$198.90
Purchase #2	$19.48	8.104%	$21.0587	$21.06	$21.05	$21.10
Purchase #3	$20.39	5.427%	$21.4966	$21.50	$21.50	$21.50
Purchase #4	$185.63	12.121%	$208.1302	$208.13	$208.15	$208.10
Purchase #5	$156.90	7.662%	$168.9217	$168.92	$168.90	$168.90
Purchase #6	$168.53	3.113%	$173.7763	$173.78	$173.80	$173.80
Purchase #7	$56.86	7.239%	$60.9761	$60.98	$61.00	$61.00
7 purchase totals =	$792.56		$853.2590	$853.27	$853.30	$853.30