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	$43.94	4.415%	$45.88	$45.88	$45.90	$45.90
Purchase #2	$196.39	11.689%	$219.346	$219.35	$219.35	$219.30
Purchase #3	$114.33	3.807%	$118.6825	$118.68	$118.70	$118.70
Purchase #4	$207.53	8.362%	$224.8837	$224.88	$224.90	$224.90
Purchase #5	$212.57	5.182%	$223.5854	$223.59	$223.60	$223.60
Purchase #6	$98.89	10.276%	$109.0519	$109.05	$109.05	$109.10
Purchase #7	$135.60	10.708%	$150.12	$150.12	$150.10	$150.10
7 purchase totals =	$1,009.25		$1,091.5495	$1,091.55	$1,091.60	$1,091.60