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	$166.64	9.485%	$182.4458	$182.45	$182.45	$182.40
Purchase #2	$105.33	4.196%	$109.7496	$109.75	$109.75	$109.70
Purchase #3	$188.68	5.850%	$199.7178	$199.72	$199.70	$199.70
Purchase #4	$146.71	3.641%	$152.0517	$152.05	$152.05	$152.10
Purchase #5	$56.50	10.290%	$62.3139	$62.31	$62.30	$62.30
Purchase #6	$127.45	5.230%	$134.1156	$134.12	$134.10	$134.10
Purchase #7	$183.44	8.392%	$198.8343	$198.83	$198.85	$198.80
7 purchase totals =	$974.75		$1,039.2287	$1,039.23	$1,039.20	$1,039.10