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	$171.31	7.570%	$184.2782	$184.28	$184.30	$184.30
Purchase #2	$220.85	6.162%	$234.4588	$234.46	$234.45	$234.50
Purchase #3	$54.71	11.869%	$61.2035	$61.20	$61.20	$61.20
Purchase #4	$154.70	9.145%	$168.8473	$168.85	$168.85	$168.80
Purchase #5	$237.88	9.165%	$259.6817	$259.68	$259.70	$259.70
Purchase #6	$117.38	9.222%	$128.2048	$128.20	$128.20	$128.20
Purchase #7	$142.60	5.461%	$150.3874	$150.39	$150.40	$150.40
7 purchase totals =	$1,099.43		$1,187.0617	$1,187.06	$1,187.10	$1,187.10