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	$58.69	5.805%	$62.097	$62.10	$62.10	$62.10
Purchase #2	$89.35	12.580%	$100.5902	$100.59	$100.60	$100.60
Purchase #3	$245.90	9.742%	$269.8556	$269.86	$269.85	$269.90
Purchase #4	$19.84	12.157%	$22.2519	$22.25	$22.25	$22.30
Purchase #5	$158.53	12.364%	$178.1306	$178.13	$178.15	$178.10
Purchase #6	$150.33	11.330%	$167.3624	$167.36	$167.35	$167.40
Purchase #7	$164.47	11.341%	$183.1225	$183.12	$183.10	$183.10
7 purchase totals =	$887.11		$983.4102	$983.41	$983.40	$983.50