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	$136.31	7.566%	$146.6232	$146.62	$146.60	$146.60
Purchase #2	$181.88	5.501%	$191.8852	$191.89	$191.90	$191.90
Purchase #3	$92.63	4.212%	$96.5316	$96.53	$96.55	$96.50
Purchase #4	$91.30	8.857%	$99.3864	$99.39	$99.40	$99.40
Purchase #5	$232.93	5.642%	$246.0719	$246.07	$246.05	$246.10
Purchase #6	$163.39	10.859%	$181.1325	$181.13	$181.15	$181.10
Purchase #7	$209.54	10.404%	$231.3405	$231.34	$231.35	$231.30
7 purchase totals =	$1,107.98		$1,192.9713	$1,192.97	$1,193.00	$1,192.90