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	$160.73	11.444%	$179.1239	$179.12	$179.10	$179.10
Purchase #2	$140.83	12.517%	$158.4577	$158.46	$158.45	$158.50
Purchase #3	$39.98	5.714%	$42.2645	$42.26	$42.25	$42.30
Purchase #4	$147.71	11.588%	$164.8266	$164.83	$164.85	$164.80
Purchase #5	$131.86	8.216%	$142.6936	$142.69	$142.70	$142.70
Purchase #6	$209.56	6.322%	$222.8084	$222.81	$222.80	$222.80
Purchase #7	$14.92	7.676%	$16.0653	$16.07	$16.05	$16.10
7 purchase totals =	$845.59		$926.2400	$926.24	$926.20	$926.30