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	$55.89	10.712%	$61.8769	$61.88	$61.90	$61.90
Purchase #2	$234.35	10.595%	$259.1794	$259.18	$259.20	$259.20
Purchase #3	$105.30	7.768%	$113.4797	$113.48	$113.50	$113.50
Purchase #4	$211.26	5.850%	$223.6187	$223.62	$223.60	$223.60
Purchase #5	$136.98	6.386%	$145.7275	$145.73	$145.75	$145.70
Purchase #6	$92.48	12.776%	$104.2952	$104.30	$104.30	$104.30
Purchase #7	$185.75	13.191%	$210.2523	$210.25	$210.25	$210.30
7 purchase totals =	$1,022.01		$1,118.4297	$1,118.44	$1,118.50	$1,118.50