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	$65.93	9.474%	$72.1762	$72.18	$72.20	$72.20
Purchase #2	$40.41	7.768%	$43.549	$43.55	$43.55	$43.50
Purchase #3	$174.86	9.827%	$192.0435	$192.04	$192.05	$192.00
Purchase #4	$158.69	10.247%	$174.951	$174.95	$174.95	$175.00
Purchase #5	$24.61	5.263%	$25.9052	$25.91	$25.90	$25.90
Purchase #6	$157.76	5.872%	$167.0237	$167.02	$167.00	$167.00
Purchase #7	$159.85	7.706%	$172.168	$172.17	$172.15	$172.20
7 purchase totals =	$782.11		$847.8166	$847.82	$847.80	$847.80