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	$214.48	6.247%	$227.8786	$227.88	$227.90	$227.90
Purchase #2	$169.31	9.823%	$185.9413	$185.94	$185.95	$185.90
Purchase #3	$233.31	9.127%	$254.6042	$254.60	$254.60	$254.60
Purchase #4	$222.90	12.270%	$250.2498	$250.25	$250.25	$250.20
Purchase #5	$85.71	4.260%	$89.3612	$89.36	$89.35	$89.40
Purchase #6	$93.34	12.349%	$104.8666	$104.87	$104.85	$104.90
Purchase #7	$224.44	6.841%	$239.7939	$239.79	$239.80	$239.80
7 purchase totals =	$1,243.49		$1,352.6956	$1,352.69	$1,352.70	$1,352.70