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	$109.88	4.422%	$114.7389	$114.74	$114.75	$114.70
Purchase #2	$155.53	7.203%	$166.7328	$166.73	$166.75	$166.70
Purchase #3	$142.44	3.276%	$147.1063	$147.11	$147.10	$147.10
Purchase #4	$155.57	8.586%	$168.9272	$168.93	$168.95	$168.90
Purchase #5	$153.85	9.778%	$168.8935	$168.89	$168.90	$168.90
Purchase #6	$173.73	8.317%	$188.1791	$188.18	$188.20	$188.20
Purchase #7	$147.85	11.234%	$164.4595	$164.46	$164.45	$164.50
7 purchase totals =	$1,038.85		$1,119.0373	$1,119.04	$1,119.10	$1,119.00