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	$70.40	12.119%	$78.9318	$78.93	$78.95	$78.90
Purchase #2	$174.25	5.212%	$183.3319	$183.33	$183.35	$183.30
Purchase #3	$216.57	12.322%	$243.2558	$243.26	$243.25	$243.30
Purchase #4	$91.38	7.603%	$98.3276	$98.33	$98.35	$98.30
Purchase #5	$166.97	6.316%	$177.5158	$177.52	$177.50	$177.50
Purchase #6	$56.84	9.765%	$62.3904	$62.39	$62.40	$62.40
Purchase #7	$245.48	5.708%	$259.492	$259.49	$259.50	$259.50
7 purchase totals =	$1,021.89		$1,103.2453	$1,103.25	$1,103.30	$1,103.20