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	$143.46	6.155%	$152.29	$152.29	$152.30	$152.30
Purchase #2	$166.90	7.848%	$179.9983	$180.00	$180.00	$180.00
Purchase #3	$41.89	11.114%	$46.5457	$46.55	$46.55	$46.50
Purchase #4	$218.99	3.276%	$226.1641	$226.16	$226.15	$226.20
Purchase #5	$184.76	8.539%	$200.5367	$200.54	$200.55	$200.50
Purchase #6	$177.54	5.290%	$186.9319	$186.93	$186.95	$186.90
Purchase #7	$40.85	4.139%	$42.5408	$42.54	$42.55	$42.50
7 purchase totals =	$974.39		$1,035.0075	$1,035.01	$1,035.05	$1,034.90