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	$185.45	12.752%	$209.0986	$209.10	$209.10	$209.10
Purchase #2	$65.85	10.238%	$72.5917	$72.59	$72.60	$72.60
Purchase #3	$135.72	12.171%	$152.2385	$152.24	$152.25	$152.20
Purchase #4	$73.29	10.222%	$80.7817	$80.78	$80.80	$80.80
Purchase #5	$86.87	11.555%	$96.9078	$96.91	$96.90	$96.90
Purchase #6	$249.89	6.736%	$266.7226	$266.72	$266.70	$266.70
Purchase #7	$156.99	11.583%	$175.1742	$175.17	$175.15	$175.20
7 purchase totals =	$954.06		$1,053.5151	$1,053.51	$1,053.50	$1,053.50