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	$61.36	4.299%	$63.9979	$64.00	$64.00	$64.00
Purchase #2	$53.85	9.785%	$59.1192	$59.12	$59.10	$59.10
Purchase #3	$17.72	3.376%	$18.3182	$18.32	$18.30	$18.30
Purchase #4	$49.42	11.629%	$55.1671	$55.17	$55.15	$55.20
Purchase #5	$133.72	6.613%	$142.5629	$142.56	$142.55	$142.60
Purchase #6	$112.36	5.834%	$118.9151	$118.92	$118.90	$118.90
Purchase #7	$21.80	10.615%	$24.1141	$24.11	$24.10	$24.10
7 purchase totals =	$450.23		$482.1945	$482.20	$482.10	$482.20