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	$32.56	3.645%	$33.7468	$33.75	$33.75	$33.70
Purchase #2	$64.44	4.387%	$67.267	$67.27	$67.25	$67.30
Purchase #3	$123.61	3.365%	$127.7695	$127.77	$127.75	$127.80
Purchase #4	$112.48	8.780%	$122.3557	$122.36	$122.35	$122.40
Purchase #5	$74.33	13.640%	$84.4686	$84.47	$84.45	$84.50
Purchase #6	$115.51	10.301%	$127.4087	$127.41	$127.40	$127.40
Purchase #7	$46.88	9.244%	$51.2136	$51.21	$51.20	$51.20
7 purchase totals =	$569.81		$614.2299	$614.24	$614.15	$614.30