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	$193.46	13.855%	$220.2639	$220.26	$220.25	$220.30
Purchase #2	$55.78	6.362%	$59.3287	$59.33	$59.35	$59.30
Purchase #3	$169.38	13.179%	$191.7026	$191.70	$191.70	$191.70
Purchase #4	$106.90	5.780%	$113.0788	$113.08	$113.10	$113.10
Purchase #5	$88.97	9.838%	$97.7229	$97.72	$97.70	$97.70
Purchase #6	$168.31	12.166%	$188.7866	$188.79	$188.80	$188.80
Purchase #7	$139.75	11.328%	$155.5809	$155.58	$155.60	$155.60
7 purchase totals =	$922.55		$1,026.4644	$1,026.46	$1,026.50	$1,026.50