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	$33.96	10.701%	$37.5941	$37.59	$37.60	$37.60
Purchase #2	$238.96	12.256%	$268.2469	$268.25	$268.25	$268.20
Purchase #3	$96.95	12.723%	$109.2849	$109.28	$109.30	$109.30
Purchase #4	$232.35	5.329%	$244.7319	$244.73	$244.75	$244.70
Purchase #5	$246.34	10.572%	$272.3831	$272.38	$272.40	$272.40
Purchase #6	$95.36	4.168%	$99.3346	$99.33	$99.35	$99.30
Purchase #7	$197.51	10.511%	$218.2703	$218.27	$218.25	$218.30
7 purchase totals =	$1,141.43		$1,249.8458	$1,249.83	$1,249.90	$1,249.80