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	$153.89	6.602%	$164.0498	$164.05	$164.05	$164.00
Purchase #2	$84.91	5.205%	$89.3296	$89.33	$89.35	$89.30
Purchase #3	$58.93	9.681%	$64.635	$64.64	$64.65	$64.60
Purchase #4	$113.31	4.617%	$118.5415	$118.54	$118.55	$118.50
Purchase #5	$241.54	4.297%	$251.919	$251.92	$251.90	$251.90
Purchase #6	$250.85	4.179%	$261.333	$261.33	$261.35	$261.30
Purchase #7	$85.76	12.435%	$96.4243	$96.42	$96.40	$96.40
7 purchase totals =	$989.19		$1,046.2322	$1,046.23	$1,046.25	$1,046.00