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	$96.83	3.311%	$100.036	$100.04	$100.05	$100.00
Purchase #2	$81.25	3.341%	$83.9646	$83.96	$83.95	$84.00
Purchase #3	$199.48	10.854%	$221.1316	$221.13	$221.15	$221.10
Purchase #4	$133.79	3.685%	$138.7202	$138.72	$138.70	$138.70
Purchase #5	$243.39	10.237%	$268.3058	$268.31	$268.30	$268.30
Purchase #6	$135.79	9.222%	$148.3126	$148.31	$148.30	$148.30
Purchase #7	$132.65	4.833%	$139.061	$139.06	$139.05	$139.10
7 purchase totals =	$1,023.18		$1,099.5318	$1,099.53	$1,099.50	$1,099.50