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	$182.69	8.688%	$198.5621	$198.56	$198.55	$198.60
Purchase #2	$120.64	13.170%	$136.5283	$136.53	$136.55	$136.50
Purchase #3	$175.44	9.228%	$191.6296	$191.63	$191.65	$191.60
Purchase #4	$148.96	6.248%	$158.267	$158.27	$158.25	$158.30
Purchase #5	$117.90	10.402%	$130.164	$130.16	$130.15	$130.20
Purchase #6	$128.73	12.687%	$145.062	$145.06	$145.05	$145.10
Purchase #7	$171.47	5.736%	$181.3055	$181.31	$181.30	$181.30
7 purchase totals =	$1,045.83		$1,141.5185	$1,141.52	$1,141.50	$1,141.60