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	$113.64	5.555%	$119.9527	$119.95	$119.95	$120.00
Purchase #2	$229.36	6.141%	$243.445	$243.45	$243.45	$243.40
Purchase #3	$162.33	10.831%	$179.912	$179.91	$179.90	$179.90
Purchase #4	$86.31	5.328%	$90.9086	$90.91	$90.90	$90.90
Purchase #5	$185.72	5.653%	$196.2188	$196.22	$196.20	$196.20
Purchase #6	$116.62	10.123%	$128.4254	$128.43	$128.45	$128.40
Purchase #7	$121.98	12.237%	$136.9067	$136.91	$136.90	$136.90
7 purchase totals =	$1,015.96		$1,095.7692	$1,095.78	$1,095.75	$1,095.70