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	$24.43	13.158%	$27.6445	$27.64	$27.65	$27.60
Purchase #2	$74.32	5.743%	$78.5882	$78.59	$78.60	$78.60
Purchase #3	$89.38	6.540%	$95.2255	$95.23	$95.25	$95.20
Purchase #4	$49.31	5.830%	$52.1848	$52.18	$52.20	$52.20
Purchase #5	$63.62	11.787%	$71.1189	$71.12	$71.10	$71.10
Purchase #6	$18.69	13.839%	$21.2765	$21.28	$21.30	$21.30
Purchase #7	$36.76	4.528%	$38.4245	$38.42	$38.40	$38.40
7 purchase totals =	$356.51		$384.4629	$384.46	$384.50	$384.40