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	$115.34	3.240%	$119.077	$119.08	$119.10	$119.10
Purchase #2	$250.39	3.807%	$259.9223	$259.92	$259.90	$259.90
Purchase #3	$164.59	9.512%	$180.2458	$180.25	$180.25	$180.20
Purchase #4	$55.76	3.549%	$57.7389	$57.74	$57.75	$57.70
Purchase #5	$164.96	3.824%	$171.2681	$171.27	$171.25	$171.30
Purchase #6	$203.85	12.534%	$229.4006	$229.40	$229.40	$229.40
Purchase #7	$41.95	4.505%	$43.8398	$43.84	$43.85	$43.80
7 purchase totals =	$996.84		$1,061.4925	$1,061.50	$1,061.50	$1,061.40