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	$207.75	6.488%	$221.2288	$221.23	$221.25	$221.20
Purchase #2	$90.99	8.641%	$98.8524	$98.85	$98.85	$98.90
Purchase #3	$216.31	12.383%	$243.0957	$243.10	$243.10	$243.10
Purchase #4	$218.95	6.689%	$233.5956	$233.60	$233.60	$233.60
Purchase #5	$80.37	6.241%	$85.3859	$85.39	$85.40	$85.40
Purchase #6	$52.39	11.330%	$58.3258	$58.33	$58.35	$58.30
Purchase #7	$95.83	9.494%	$104.9281	$104.93	$104.95	$104.90
7 purchase totals =	$962.59		$1,045.4123	$1,045.43	$1,045.50	$1,045.40