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	$161.32	11.769%	$180.3058	$180.31	$180.30	$180.30
Purchase #2	$174.62	4.558%	$182.5792	$182.58	$182.60	$182.60
Purchase #3	$171.66	4.790%	$179.8825	$179.88	$179.90	$179.90
Purchase #4	$77.74	5.511%	$82.0243	$82.02	$82.00	$82.00
Purchase #5	$36.36	3.796%	$37.7402	$37.74	$37.75	$37.70
Purchase #6	$196.44	13.472%	$222.9044	$222.90	$222.90	$222.90
Purchase #7	$206.26	5.715%	$218.0478	$218.05	$218.05	$218.00
7 purchase totals =	$1,024.40		$1,103.4842	$1,103.48	$1,103.50	$1,103.40