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	$132.71	10.359%	$146.4574	$146.46	$146.45	$146.50
Purchase #2	$145.56	7.731%	$156.8132	$156.81	$156.80	$156.80
Purchase #3	$72.40	13.363%	$82.0748	$82.07	$82.05	$82.10
Purchase #4	$191.27	7.473%	$205.5636	$205.56	$205.55	$205.60
Purchase #5	$151.94	6.819%	$162.3008	$162.30	$162.30	$162.30
Purchase #6	$185.68	3.257%	$191.7276	$191.73	$191.75	$191.70
Purchase #7	$119.65	3.153%	$123.4226	$123.42	$123.40	$123.40
7 purchase totals =	$999.21		$1,068.3600	$1,068.35	$1,068.30	$1,068.40