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	$221.57	9.249%	$242.063	$242.06	$242.05	$242.10
Purchase #2	$118.25	11.478%	$131.8227	$131.82	$131.80	$131.80
Purchase #3	$179.72	4.631%	$188.0428	$188.04	$188.05	$188.00
Purchase #4	$21.75	10.600%	$24.0555	$24.06	$24.05	$24.10
Purchase #5	$170.41	12.411%	$191.5596	$191.56	$191.55	$191.60
Purchase #6	$243.77	7.581%	$262.2502	$262.25	$262.25	$262.30
Purchase #7	$98.31	9.320%	$107.4725	$107.47	$107.45	$107.50
7 purchase totals =	$1,053.78		$1,147.2663	$1,147.26	$1,147.20	$1,147.40