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	$222.50	12.252%	$249.7607	$249.76	$249.75	$249.80
Purchase #2	$25.71	11.219%	$28.5944	$28.59	$28.60	$28.60
Purchase #3	$85.25	6.486%	$90.7793	$90.78	$90.80	$90.80
Purchase #4	$60.26	11.398%	$67.1284	$67.13	$67.15	$67.10
Purchase #5	$241.43	9.279%	$263.8323	$263.83	$263.85	$263.80
Purchase #6	$125.72	13.177%	$142.2861	$142.29	$142.30	$142.30
Purchase #7	$185.71	13.770%	$211.2823	$211.28	$211.30	$211.30
7 purchase totals =	$946.58		$1,053.6635	$1,053.66	$1,053.75	$1,053.70