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	$182.75	10.187%	$201.3667	$201.37	$201.35	$201.40
Purchase #2	$38.63	3.692%	$40.0562	$40.06	$40.05	$40.10
Purchase #3	$165.25	4.529%	$172.7342	$172.73	$172.75	$172.70
Purchase #4	$99.61	11.544%	$111.109	$111.11	$111.10	$111.10
Purchase #5	$65.49	10.589%	$72.4247	$72.42	$72.40	$72.40
Purchase #6	$92.76	10.842%	$102.817	$102.82	$102.80	$102.80
Purchase #7	$98.70	9.365%	$107.9433	$107.94	$107.95	$107.90
7 purchase totals =	$743.19		$808.4511	$808.45	$808.40	$808.40