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	$174.39	6.196%	$185.1952	$185.20	$185.20	$185.20
Purchase #2	$233.66	6.783%	$249.5092	$249.51	$249.50	$249.50
Purchase #3	$100.43	8.774%	$109.2417	$109.24	$109.25	$109.20
Purchase #4	$158.50	4.373%	$165.4312	$165.43	$165.45	$165.40
Purchase #5	$41.62	6.781%	$44.4423	$44.44	$44.45	$44.40
Purchase #6	$35.79	10.289%	$39.4724	$39.47	$39.45	$39.50
Purchase #7	$197.25	12.359%	$221.6281	$221.63	$221.65	$221.60
7 purchase totals =	$941.64		$1,014.9201	$1,014.92	$1,014.95	$1,014.80