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	$86.53	11.801%	$96.7414	$96.74	$96.75	$96.70
Purchase #2	$139.89	3.145%	$144.2895	$144.29	$144.30	$144.30
Purchase #3	$233.53	13.731%	$265.596	$265.60	$265.60	$265.60
Purchase #4	$218.93	13.650%	$248.8139	$248.81	$248.80	$248.80
Purchase #5	$187.58	4.664%	$196.3287	$196.33	$196.35	$196.30
Purchase #6	$89.64	9.855%	$98.474	$98.47	$98.45	$98.50
Purchase #7	$61.39	13.690%	$69.7943	$69.79	$69.80	$69.80
7 purchase totals =	$1,017.49		$1,120.0378	$1,120.03	$1,120.05	$1,120.00