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	$191.83	4.728%	$200.8997	$200.90	$200.90	$200.90
Purchase #2	$124.42	11.551%	$138.7918	$138.79	$138.80	$138.80
Purchase #3	$40.78	11.245%	$45.3657	$45.37	$45.35	$45.40
Purchase #4	$73.37	13.683%	$83.4092	$83.41	$83.40	$83.40
Purchase #5	$168.93	8.768%	$183.7418	$183.74	$183.75	$183.70
Purchase #6	$242.39	11.498%	$270.26	$270.26	$270.25	$270.30
Purchase #7	$225.38	3.517%	$233.3066	$233.31	$233.30	$233.30
7 purchase totals =	$1,067.10		$1,155.7748	$1,155.78	$1,155.75	$1,155.80