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	$176.32	4.705%	$184.6159	$184.62	$184.60	$184.60
Purchase #2	$123.54	11.406%	$137.631	$137.63	$137.65	$137.60
Purchase #3	$106.84	10.833%	$118.414	$118.41	$118.40	$118.40
Purchase #4	$111.33	3.580%	$115.3156	$115.32	$115.30	$115.30
Purchase #5	$243.64	7.701%	$262.4027	$262.40	$262.40	$262.40
Purchase #6	$149.27	12.737%	$168.2825	$168.28	$168.30	$168.30
Purchase #7	$115.92	6.154%	$123.0537	$123.05	$123.05	$123.10
7 purchase totals =	$1,026.86		$1,109.7154	$1,109.71	$1,109.70	$1,109.70