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	$167.82	9.657%	$184.0264	$184.03	$184.05	$184.00
Purchase #2	$86.90	13.141%	$98.3195	$98.32	$98.30	$98.30
Purchase #3	$73.37	12.490%	$82.5339	$82.53	$82.55	$82.50
Purchase #4	$230.36	4.618%	$240.998	$241.00	$241.00	$241.00
Purchase #5	$175.93	5.665%	$185.8964	$185.90	$185.90	$185.90
Purchase #6	$235.43	6.748%	$251.3168	$251.32	$251.30	$251.30
Purchase #7	$79.90	12.300%	$89.7277	$89.73	$89.75	$89.70
7 purchase totals =	$1,049.71		$1,132.8187	$1,132.83	$1,132.85	$1,132.70