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	$232.29	7.562%	$249.8558	$249.86	$249.85	$249.90
Purchase #2	$154.33	7.708%	$166.2258	$166.23	$166.25	$166.20
Purchase #3	$157.84	4.708%	$165.2711	$165.27	$165.25	$165.30
Purchase #4	$136.74	4.175%	$142.4489	$142.45	$142.45	$142.40
Purchase #5	$108.74	4.817%	$113.978	$113.98	$114.00	$114.00
Purchase #6	$151.60	9.696%	$166.2991	$166.30	$166.30	$166.30
Purchase #7	$80.37	7.612%	$86.4878	$86.49	$86.50	$86.50
7 purchase totals =	$1,021.91		$1,090.5665	$1,090.58	$1,090.60	$1,090.60