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	$174.89	3.831%	$181.59	$181.59	$181.60	$181.60
Purchase #2	$73.72	11.241%	$82.0069	$82.01	$82.00	$82.00
Purchase #3	$181.69	6.547%	$193.5852	$193.59	$193.60	$193.60
Purchase #4	$192.27	8.410%	$208.4399	$208.44	$208.45	$208.40
Purchase #5	$235.98	13.717%	$268.3494	$268.35	$268.35	$268.30
Purchase #6	$250.29	12.180%	$280.7753	$280.78	$280.80	$280.80
Purchase #7	$173.35	12.780%	$195.5041	$195.50	$195.50	$195.50
7 purchase totals =	$1,282.19		$1,410.2508	$1,410.26	$1,410.30	$1,410.20