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	$73.73	11.761%	$82.4014	$82.40	$82.40	$82.40
Purchase #2	$103.38	6.459%	$110.0573	$110.06	$110.05	$110.10
Purchase #3	$236.78	3.305%	$244.6056	$244.61	$244.60	$244.60
Purchase #4	$81.34	3.786%	$84.4195	$84.42	$84.40	$84.40
Purchase #5	$129.40	10.513%	$143.0038	$143.00	$143.00	$143.00
Purchase #6	$180.38	6.119%	$191.4175	$191.42	$191.40	$191.40
Purchase #7	$146.60	11.147%	$162.9415	$162.94	$162.95	$162.90
7 purchase totals =	$951.61		$1,018.8466	$1,018.85	$1,018.80	$1,018.80