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	$245.29	7.418%	$263.4856	$263.49	$263.50	$263.50
Purchase #2	$188.32	5.533%	$198.7397	$198.74	$198.75	$198.70
Purchase #3	$59.39	10.440%	$65.5903	$65.59	$65.60	$65.60
Purchase #4	$82.93	12.752%	$93.5052	$93.51	$93.50	$93.50
Purchase #5	$241.26	11.177%	$268.2256	$268.23	$268.25	$268.20
Purchase #6	$35.98	9.674%	$39.4607	$39.46	$39.45	$39.50
Purchase #7	$240.38	11.166%	$267.2208	$267.22	$267.20	$267.20
7 purchase totals =	$1,093.55		$1,196.2279	$1,196.24	$1,196.25	$1,196.20