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	$81.99	3.698%	$85.022	$85.02	$85.00	$85.00
Purchase #2	$208.52	13.770%	$237.2332	$237.23	$237.25	$237.20
Purchase #3	$86.97	13.821%	$98.9901	$98.99	$99.00	$99.00
Purchase #4	$178.33	10.141%	$196.4144	$196.41	$196.40	$196.40
Purchase #5	$195.55	7.273%	$209.7724	$209.77	$209.75	$209.80
Purchase #6	$96.55	3.574%	$100.0007	$100.00	$100.00	$100.00
Purchase #7	$155.63	8.112%	$168.2547	$168.25	$168.25	$168.30
7 purchase totals =	$1,003.54		$1,095.6875	$1,095.67	$1,095.65	$1,095.70