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	$41.72	7.443%	$44.8252	$44.83	$44.85	$44.80
Purchase #2	$147.83	12.789%	$166.736	$166.74	$166.75	$166.70
Purchase #3	$179.81	11.556%	$200.5888	$200.59	$200.60	$200.60
Purchase #4	$93.41	3.153%	$96.3552	$96.36	$96.35	$96.40
Purchase #5	$224.28	6.825%	$239.5871	$239.59	$239.60	$239.60
Purchase #6	$44.72	13.781%	$50.8829	$50.88	$50.90	$50.90
Purchase #7	$199.81	12.616%	$225.018	$225.02	$225.00	$225.00
7 purchase totals =	$931.58		$1,023.9932	$1,024.01	$1,024.05	$1,024.00