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	$250.66	4.688%	$262.4109	$262.41	$262.40	$262.40
Purchase #2	$241.41	5.481%	$254.6417	$254.64	$254.65	$254.60
Purchase #3	$99.40	9.666%	$109.008	$109.01	$109.00	$109.00
Purchase #4	$150.70	3.152%	$155.4501	$155.45	$155.45	$155.50
Purchase #5	$161.36	12.564%	$181.6333	$181.63	$181.65	$181.60
Purchase #6	$84.79	13.587%	$96.3104	$96.31	$96.30	$96.30
Purchase #7	$77.89	9.402%	$85.2132	$85.21	$85.20	$85.20
7 purchase totals =	$1,066.21		$1,144.6676	$1,144.66	$1,144.65	$1,144.60