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	$87.27	13.821%	$99.3316	$99.33	$99.35	$99.30
Purchase #2	$181.51	8.498%	$196.9347	$196.93	$196.95	$196.90
Purchase #3	$189.65	4.790%	$198.7342	$198.73	$198.75	$198.70
Purchase #4	$53.33	5.343%	$56.1794	$56.18	$56.20	$56.20
Purchase #5	$19.29	3.213%	$19.9098	$19.91	$19.90	$19.90
Purchase #6	$148.43	10.665%	$164.2601	$164.26	$164.25	$164.30
Purchase #7	$156.90	7.224%	$168.2345	$168.23	$168.25	$168.20
7 purchase totals =	$836.38		$903.5843	$903.57	$903.65	$903.50