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	$109.69	13.639%	$124.6506	$124.65	$124.65	$124.70
Purchase #2	$18.32	9.648%	$20.0875	$20.09	$20.10	$20.10
Purchase #3	$185.50	3.388%	$191.7847	$191.78	$191.80	$191.80
Purchase #4	$90.55	12.787%	$102.1286	$102.13	$102.15	$102.10
Purchase #5	$41.31	3.211%	$42.6365	$42.64	$42.65	$42.60
Purchase #6	$248.31	7.149%	$266.0617	$266.06	$266.05	$266.10
Purchase #7	$184.27	7.717%	$198.4901	$198.49	$198.50	$198.50
7 purchase totals =	$877.95		$945.8397	$945.84	$945.90	$945.90