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	$168.58	12.658%	$189.9189	$189.92	$189.90	$189.90
Purchase #2	$90.43	9.640%	$99.1475	$99.15	$99.15	$99.10
Purchase #3	$117.87	7.446%	$126.6466	$126.65	$126.65	$126.60
Purchase #4	$114.64	11.348%	$127.6493	$127.65	$127.65	$127.60
Purchase #5	$198.93	11.262%	$221.3335	$221.33	$221.35	$221.30
Purchase #6	$26.49	6.210%	$28.135	$28.14	$28.15	$28.10
Purchase #7	$216.82	4.408%	$226.3774	$226.38	$226.40	$226.40
7 purchase totals =	$933.76		$1,019.2082	$1,019.22	$1,019.25	$1,019.00