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	$165.54	5.145%	$174.057	$174.06	$174.05	$174.10
Purchase #2	$48.73	12.218%	$54.6838	$54.68	$54.70	$54.70
Purchase #3	$184.94	7.360%	$198.5516	$198.55	$198.55	$198.60
Purchase #4	$240.65	8.498%	$261.1004	$261.10	$261.10	$261.10
Purchase #5	$231.59	3.660%	$240.0662	$240.07	$240.05	$240.10
Purchase #6	$153.35	12.706%	$172.8347	$172.83	$172.85	$172.80
Purchase #7	$72.36	10.573%	$80.0106	$80.01	$80.00	$80.00
7 purchase totals =	$1,097.16		$1,181.3043	$1,181.30	$1,181.30	$1,181.40