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	$83.80	5.327%	$88.264	$88.26	$88.25	$88.30
Purchase #2	$89.25	3.511%	$92.3836	$92.38	$92.40	$92.40
Purchase #3	$136.85	5.392%	$144.229	$144.23	$144.25	$144.20
Purchase #4	$226.65	12.196%	$254.2922	$254.29	$254.30	$254.30
Purchase #5	$176.69	10.265%	$194.8272	$194.83	$194.85	$194.80
Purchase #6	$244.91	13.441%	$277.8284	$277.83	$277.85	$277.80
Purchase #7	$78.70	4.327%	$82.1053	$82.11	$82.10	$82.10
7 purchase totals =	$1,036.85		$1,133.9297	$1,133.93	$1,134.00	$1,133.90