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	$241.39	5.577%	$254.8523	$254.85	$254.85	$254.90
Purchase #2	$140.41	10.498%	$155.1502	$155.15	$155.15	$155.20
Purchase #3	$89.94	7.359%	$96.5587	$96.56	$96.55	$96.60
Purchase #4	$120.63	6.185%	$128.091	$128.09	$128.10	$128.10
Purchase #5	$189.86	5.833%	$200.9345	$200.93	$200.95	$200.90
Purchase #6	$33.33	6.338%	$35.4425	$35.44	$35.45	$35.40
Purchase #7	$147.44	13.514%	$167.365	$167.37	$167.35	$167.40
7 purchase totals =	$963.00		$1,038.3942	$1,038.39	$1,038.40	$1,038.50