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	$62.49	4.437%	$65.2627	$65.26	$65.25	$65.30
Purchase #2	$194.38	7.681%	$209.3103	$209.31	$209.30	$209.30
Purchase #3	$215.42	11.818%	$240.8783	$240.88	$240.90	$240.90
Purchase #4	$173.49	11.153%	$192.8393	$192.84	$192.85	$192.80
Purchase #5	$82.73	13.180%	$93.6338	$93.63	$93.65	$93.60
Purchase #6	$189.73	4.611%	$198.4785	$198.48	$198.50	$198.50
Purchase #7	$82.36	11.196%	$91.581	$91.58	$91.60	$91.60
7 purchase totals =	$1,000.60		$1,091.9839	$1,091.98	$1,092.05	$1,092.00