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	$150.33	6.270%	$159.7557	$159.76	$159.75	$159.80
Purchase #2	$7.28	10.658%	$8.0559	$8.06	$8.05	$8.10
Purchase #3	$95.31	9.314%	$104.1872	$104.19	$104.20	$104.20
Purchase #4	$135.61	10.246%	$149.5046	$149.50	$149.50	$149.50
Purchase #5	$164.47	11.132%	$182.7788	$182.78	$182.80	$182.80
Purchase #6	$199.56	6.125%	$211.7831	$211.78	$211.80	$211.80
Purchase #7	$177.50	12.855%	$200.3176	$200.32	$200.30	$200.30
7 purchase totals =	$930.06		$1,016.3829	$1,016.39	$1,016.40	$1,016.50