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	$128.91	3.289%	$133.1498	$133.15	$133.15	$133.10
Purchase #2	$84.69	9.196%	$92.4781	$92.48	$92.50	$92.50
Purchase #3	$238.49	12.216%	$267.6239	$267.62	$267.60	$267.60
Purchase #4	$167.91	3.620%	$173.9883	$173.99	$174.00	$174.00
Purchase #5	$191.49	13.238%	$216.8394	$216.84	$216.85	$216.80
Purchase #6	$95.56	5.447%	$100.7652	$100.77	$100.75	$100.80
Purchase #7	$95.46	6.413%	$101.5818	$101.58	$101.60	$101.60
7 purchase totals =	$1,002.51		$1,086.4265	$1,086.43	$1,086.45	$1,086.40